nodejs / node-addon-examples

Node.js C++ addon examples from http://nodejs.org/docs/latest/api/addons.html

Node.js Addon Examples

A repository of Node.js Addons examples.

Implementations of examples are named either after Node.js versions (node_0.10, node_0.12, etc), or Node.js addon implementation APIs:

• nan: C++-based abstraction between Node and direct V8 APIs.
• Node-API: C-based API guaranteeing ABI stability across different node versions as well as JavaScript engines. (Node-API was previously known as N-API.)
• node-addon-api: header-only C++ wrapper classes which simplify the use of the C-based Node-API.
• node-addon-api-addon-class: Similar to node-addon-api, but deriving from the Napi::Addon class. 1_hello_world provides an example.

Implementations against unsupported versions of Node.js are provided for completeness and historical context. They are not maintained.

The examples are primarily maintained for Node-API and node-addon-api and as outlined in the Node.js documentation, unless there is a need for direct access to functionality which is not exposed by Node-API, use Node-API.

The Node-API Resource offers an excellent orientation and tips for developers just getting started with Node-API and node-addon-api.

Usage

The directory structure is as follows:

REPO_ROOT
├── test_all.js
├── package.json
├── README.md
└── src
    ├── 1-getting-started
    │   ├── example1
    │   │   ├── nan
    │   │   ├── node-addon-api
    │   │   └── napi
    │   ├── example2
    │   └── example3
    ├── 2-js-to-native-conversion
    ├── 3-context-awareness
    ├── 4-references-and-handle-scope
    ├── 5-async-work
    ├── 6-threadsafe-function
    ├── 7-events
    └── 8-tooling

In each example's implementation subdirectory, run

npm install
node ./

to see the example in action.

node-addon-examples's Issues

Methods not returning after throwing Javascript exception

In the "6_object_wrap_example/node-addon-api", I tried to test what would happen when calling the constructor without arguments and I noticed that the actual exception thrown ("A number was expected") is different from the one in the code ("Number expected").

According to node-addon-api docs, when C++ exceptions are disabled you need to return immediately after calling ThrowAsJavaScriptException. So I would expect something like:

if (length <= 0 || !info[0].IsNumber()) {
    Napi::TypeError::New(env, "Number expected").ThrowAsJavaScriptException();
    return;
}

I think that the exception thrown is not the one from line 28 of myobject.cc, but another one thrown automatically when trying to convert the parameter to a number.

I tried to move one step further (following this tutorial) and unwrapping a Javascript object, and I get a segmentation fault when using the constructor without arguments because the code is not stopping after reaching the line with ThrowAsJavaScriptException.

Request: async example

An example that calls a callback asynchronously would be very valuable.

I imagine getting async behaviour correct is what most addon developers are going to be worried about, i.e. not blocking the Node event loop.
I at least really don't know where to start with it.

Failed to compile 2_function_arguments with node v.0.10

user1@ubuntu:~/node-addon-examples/2_function_arguments/node_0.10$ npm install

[email protected] install /home/user1/node-addon-examples/2_function_arguments/node_0.10
node-gyp rebuild

make: Entering directory /home/user1/node-addon-examples/2_function_arguments/node_0.10/build' CXX(target) Release/obj.target/addon/addon.o ../addon.cc:5:16: error: ‘FunctionCallbackInfo’ in namespace ‘v8’ does not name a type ../addon.cc:5:20: error: ISO C++ forbids declaration of ‘parameter’ with no type [-fpermissive] ../addon.cc:5:40: error: expected ‘,’ or ‘...’ before ‘<’ token ../addon.cc: In function ‘void Add(int)’: ../addon.cc:7:28: error: no matching function for call to ‘v8::HandleScope::HandleScope(v8::Isolate*&)’ ../addon.cc:7:28: note: candidates are: /home/user1/.node-gyp/0.10.40/deps/v8/include/v8.h:473:3: note: v8::HandleScope::HandleScope(const v8::HandleScope&) /home/user1/.node-gyp/0.10.40/deps/v8/include/v8.h:473:3: note: no known conversion for argument 1 from ‘v8::Isolate*’ to ‘const v8::HandleScope&’ /home/user1/.node-gyp/0.10.40/deps/v8/include/v8.h:448:3: note: v8::HandleScope::HandleScope() /home/user1/.node-gyp/0.10.40/deps/v8/include/v8.h:448:3: note: candidate expects 0 arguments, 1 provided ../addon.cc:9:7: error: ‘args’ was not declared in this scope ../addon.cc:14:8: error: ‘args’ was not declared in this scope ../addon.cc:19:17: error: ‘args’ was not declared in this scope ../addon.cc: In function ‘void Init(v8::Handle<v8::Object>)’: ../addon.cc:28:32: error: invalid conversion from ‘void (*)(int)’ to ‘v8::InvocationCallback {aka v8::Handle<v8::Value> (*)(const v8::Arguments&)}’ [-fpermissive] /home/user1/.node-gyp/0.10.40/deps/v8/include/v8.h:2259:34: error: initializing argument 1 of ‘static v8::Local<v8::FunctionTemplate> v8::FunctionTemplate::New(v8::InvocationCallback, v8::Handle<v8::Value>, v8::Handle<v8::Signature>)’ [-fpermissive] make: *** [Release/obj.target/addon/addon.o] Error 1 make: Leaving directory/home/user1/node-addon-examples/2_function_arguments/node_0.10/build'
gyp ERR! build error
gyp ERR! stack Error: make failed with exit code: 2
gyp ERR! stack at ChildProcess.onExit (/home/user1/.nvm/v0.10.40/lib/node_modules/npm/node_modules/node-gyp/lib/build.js:267:23)
gyp ERR! stack at ChildProcess.emit (events.js:98:17)
gyp ERR! stack at Process.ChildProcess._handle.onexit (child_process.js:820:12)
gyp ERR! System Linux 3.2.0-29-generic
gyp ERR! command "node" "/home/user1/.nvm/v0.10.40/lib/node_modules/npm/node_modules/node-gyp/bin/node-gyp.js" "rebuild"
gyp ERR! cwd /home/user1/node-addon-examples/2_function_arguments/node_0.10
gyp ERR! node -v v0.10.40
gyp ERR! node-gyp -v v1.0.1
gyp ERR! not ok

npm ERR! [email protected] install: node-gyp rebuild
npm ERR! Exit status 1
npm ERR!
npm ERR! Failed at the [email protected] install script.
npm ERR! This is most likely a problem with the function_arguments package,
npm ERR! not with npm itself.
npm ERR! Tell the author that this fails on your system:
npm ERR! node-gyp rebuild
npm ERR! You can get their info via:
npm ERR! npm owner ls function_arguments
npm ERR! There is likely additional logging output above.
npm ERR! System Linux 3.2.0-29-generic
npm ERR! command "/home/user1/.nvm/v0.10.40/bin/node" "/home/user1/.nvm/v0.10.40/bin/npm" "install"
npm ERR! cwd /home/user1/node-addon-examples/2_function_arguments/node_0.10
npm ERR! node -v v0.10.40
npm ERR! npm -v 1.4.28
npm ERR! code ELIFECYCLE
npm ERR!
npm ERR! Additional logging details can be found in:
npm ERR! /home/user1/node-addon-examples/2_function_arguments/node_0.10/npm-debug.log
npm ERR! not ok code 0

Create bindings non-invasively/non-destructively?

This may be a silly question and it may be the wrong place for it, but I think it's probably the best place for it nonetheless.

I've gone through the examples, and a variety of libraries like libxml, I generally see that the entire .cc file must be essentially re-written to look like v8 cpp. I'm curious if there isn't a way, or if maybe it's somehow implied already and I'm just not seeing it, that someone could work less invasively, without destroying the original cpp source. For example

my-addon/
-- original-src/
-- -- hello.h
-- -- hello.cc
-- src/
-- -- hello_node.cc
-- binding.gyp

Where hello.cc is some library that has absolutely no v8 code in it, but can then be included & wrapped in hello_node.cc. So for example, hello.cc would compile into some library that exported a function hello that outputs "world", you would then write all the v8 wrapper code in hello_node.cc. Right now, it looks like the idea is to go into hello.cc and rewrite the function hello in a v8-compatible manner.

Is this something that just can't be done, or that would require specific circumstances?

Thanks!

EventEmitter

Hi,

Is it possible to add another example showing how to emit events from the c++ land?

Here's an example done by bnoordhuis 2 years ago. Maybe you could rewrite it for v0.10 and v0.11?

The basic idea is to expose a c++ class which inherits from ObjectWrap and internally calls to the emit function and in the js code inherit from EventEmitter.

Need an example of using napi_create_async_work()

nodejs/node#13512 seems to indicate that we should have such an example.

node-gyp build issue

Hi,

I have been working with Node addon and everything was working great until today when I started getting issues in node-gyp build. my addon compiles successfully but hangs forever and doesn't create .node file. the last line I see in console is SOLINK_MODULE(target) Release/obj.target/something.node. It simply hangs there for ever.

I did lot of search online but couldn't find any help.

Thanks

7_factory_wrap coredumps

On node v9.4.0, node-gyp v3.6.2, [email protected], example 7_factory_wrap compiles but then coredumps.
If prototype is not set to a new one

  tpl->PrototypeTemplate()->Set(Nan::New("plusOne").ToLocalChecked(),
      Nan::New<v8::FunctionTemplate>(PlusOne)->GetFunction());

but only has the method added to it, as in 6_object_wrap

  Nan::SetPrototypeMethod(tpl, "plusOne", PlusOne);

It works. But I assume the point was to demonstrate how the prototype can be created, so I didn't send a PR.

Hello World throws "Module did not self-register" with iojs (1.4.3) on Windows 8 x64

The hello world example works for me with node 0.12, but fails with iojs 1.4.3 on Windows 8 x64.
I removed node 0.12 and verified nodejs folder was completely removed from Program Files. I then installed iojs 1.4.3 and get the following in a shell window on asking the versions.

$ node -v
v1.4.3

$ npm -v
2.6.1

I ran npm cache clean, and deleted any old .node_gyp folders in my profile to ensure there were no remnants of node 0.12. I then updated 'nan' to the latest version by npm uninstall --save nan, npm install --save nan. There were no errors from nod_gyp, but on running npm test, I get the following error.

Error: Module did not self-register.
    at Error (native)
    at Module.load (module.js:339:32)
    at Function.Module._load (module.js:294:12)
    at Module.require (module.js:349:17)
    at require (module.js:368:17)
    at bindings (C:\Users\philip\Desktop\node-addon-examples\1_hello_world\nan\node_modules\bindings\bindings.s:76:44)
    at Object.<anonymous> (C:\Users\philip\Desktop\node-addon-examples\1_hello_world\nan\hello.js:1:94)
    at Module._compile (module.js:444:26)
    at Object.Module._extensions..js (module.js:462:10)
    at Module.load (module.js:339:32)
npm ERR! Test failed.  See above for more details.

When this failed with "nan", I then tried the node_0.12 folder version that doesn't use the nan macros, but it shows the same behaviour.

Should the Hello World example work with iojs on WIndows x64, or have I perhas got some setting or old version of a library lurking not cleared?

thanks,
--philip

Requesting example of Typed Array access

As of Nan version 2.1.0 there exists Nan::TypedArrayContents, which assists in accessing Typed Arrays. See https://github.com/nodejs/nan/blob/master/doc/v8_misc.md#nantypedarraycontents

It would be very useful to have an example of how to use this. I could make the push request with a new example included so long as I was given some assistance with the coding.

Make callback with buffer as argument

Hello,

I'm having trouble making a callback and passing a Buffer as the argument.

Look at the code here:

v8::Local<v8::Function> callback;

void SetCallback(const Nan::FunctionCallbackInfo<v8::Value>& info) {
  callback = info[0].As<v8::Function>();
}

void do_callback() {
    int size = 100;
    v8::MaybeLocal<v8::Object> obj = Nan::NewBuffer(size);
    const unsigned argc = 1;
    args[1] = { obj.ToLocalChecked() };
    Nan::MakeCallback(Nan::GetCurrentContext()->Global(), callback, argc, args);
}

I always get "segmentation fault" and I do not know why..

To keep the code simple I am just intializing a new Buffer with size only..

However i would like to intialize the Buffer with data like so:

char* data =...
v8::MaybeLocal<v8::Object> obj = Nan::NewBuffer(data, size);

My goal is to callback a javascript function with a Buffer that is wrapped around an existing char pointer..

Please help.

Thank you!

Hello World example doesn't build

Trying to follow the hello world example, I get stopped at Step 5:

gyp info it worked if it ends with ok
gyp info using [email protected]
gyp info using [email protected] | darwin | x64
gyp info spawn make
gyp info spawn args [ 'BUILDTYPE=Release', '-C', 'build' ]
  CXX(target) Release/obj.target/hello/hello.o
../hello.cc:7:26: error: no member named 'New' in 'v8::String'
  NanReturnValue(String::New("world"));
                 ~~~~~~~~^
../node_modules/nan/nan.h:401:81: note: expanded from macro 'NanReturnValue'
# define NanReturnValue(value) return args.GetReturnValue().Set(_NanEnsureLocal(value))
                                                                                ^
../hello.cc:11:16: warning: 'NanSymbol' is deprecated [-Wdeprecated-declarations]
  exports->Set(NanSymbol("hello"), FunctionTemplate::New(Method)->GetFunction());
               ^
../node_modules/nan/nan.h:499:51: note: 'NanSymbol' has been explicitly marked deprecated here
  NAN_DEPRECATED NAN_INLINE v8::Local<v8::String> NanSymbol(
                                                  ^
../hello.cc:11:58: error: cannot initialize a parameter of type 'v8::Isolate *' with an lvalue of type 'void
      (const v8::FunctionCallbackInfo<v8::Value> &)'
  exports->Set(NanSymbol("hello"), FunctionTemplate::New(Method)->GetFunction());
                                                         ^~~~~~
/Users/arthurakay/.node-gyp/0.12.0/deps/v8/include/v8.h:3456:16: note: passing argument to parameter
      'isolate' here
      Isolate* isolate,
               ^
1 warning and 2 errors generated.
make: *** [Release/obj.target/hello/hello.o] Error 1
gyp ERR! build error 
gyp ERR! stack Error: `make` failed with exit code: 2
gyp ERR! stack     at ChildProcess.onExit (/usr/local/lib/node_modules/node-gyp/lib/build.js:269:23)
gyp ERR! stack     at ChildProcess.emit (events.js:110:17)
gyp ERR! stack     at Process.ChildProcess._handle.onexit (child_process.js:1067:12)
gyp ERR! System Darwin 14.1.0
gyp ERR! command "node" "/usr/local/bin/node-gyp" "build"
gyp ERR! cwd /Users/arthurakay/www/node_addons/quark
gyp ERR! node -v v0.12.0
gyp ERR! node-gyp -v v1.0.3
gyp ERR! not ok 

While I'm fairly experienced in Node.js, I'm an absolute noob in V8 and NAN. I would guess this is a Node version problem, but I was hoping someone might help clear things up for me. Thanks!

Mac OS X 10.10.2, other versions (node, etc) in the callstack above.

is NAN still the name of the game

Is NAN still the state of the art way to create Node.js addons? Looking at a repo like this:

https://github.com/nodejs/node-addon-examples/tree/master/1_hello_world

it looks like NAPI has overtaken NAN, or?

this info should go in the readme, telling users which one is the most recent version to use?

1_hello_world example => nody-gyp build failure

I am totally new to addons and node-gyp

in the 1_hello_world example

sudo node-gyp configure # works

but

sudo node-gyp build # fails

failing with these messages

gyp info it worked if it ends with ok
gyp info using [email protected]
gyp info using [email protected] | linux | x64
gyp info spawn make
gyp info spawn args [ 'BUILDTYPE=Release', '-C', 'build' ]
make: Entering directory '/home/oleg/WebstormProjects/oresoftware/replace-line/build'
  CXX(target) Release/obj.target/hello/hello.o
../hello.cc: In function ‘Nan::NAN_METHOD_RETURN_TYPE Method(Nan::NAN_METHOD_ARGS_TYPE)’:
../hello.cc:6:12: error: ‘NanScope’ was not declared in this scope
   NanScope();
            ^
../hello.cc:7:18: error: ‘New’ is not a member of ‘v8::String’
   NanReturnValue(String::New("world"));
                  ^
../hello.cc:7:38: error: ‘NanReturnValue’ was not declared in this scope
   NanReturnValue(String::New("world"));
                                      ^
../hello.cc: In function ‘void Init(v8::Handle<v8::Object>)’:
../hello.cc:11:33: error: ‘NanSymbol’ was not declared in this scope
   exports->Set(NanSymbol("hello"), FunctionTemplate::New(Method)->GetFunction());
                                 ^
../hello.cc:11:64: error: no matching function for call to ‘v8::FunctionTemplate::New(Nan::NAN_METHOD_RETURN_TYPE (&)(Nan::NAN_METHOD_ARGS_TYPE))’
   exports->Set(NanSymbol("hello"), FunctionTemplate::New(Method)->GetFunction());
                                                                ^
In file included from /home/oleg/.node-gyp/4.2.6/include/node/node.h:42:0,
                 from ../node_modules/nan/nan.h:47,
                 from ../hello.cc:1:
/home/oleg/.node-gyp/4.2.6/include/node/v8.h:4349:34: note: candidate: static v8::Local<v8::FunctionTemplate> v8::FunctionTemplate::New(v8::Isolate*, v8::FunctionCallback, v8::Local<v8::Value>, v8::Local<v8::Signature>, int)
   static Local<FunctionTemplate> New(
                                  ^
/home/oleg/.node-gyp/4.2.6/include/node/v8.h:4349:34: note:   no known conversion for argument 1 from ‘Nan::NAN_METHOD_RETURN_TYPE(Nan::NAN_METHOD_ARGS_TYPE) {aka void(const Nan::FunctionCallbackInfo<v8::Value>&)}’ to ‘v8::Isolate*’
hello.target.mk:96: recipe for target 'Release/obj.target/hello/hello.o' failed
make: *** [Release/obj.target/hello/hello.o] Error 1
make: Leaving directory '/home/oleg/WebstormProjects/oresoftware/replace-line/build'
gyp ERR! build error 
gyp ERR! stack Error: `make` failed with exit code: 2
gyp ERR! stack     at ChildProcess.onExit (/usr/local/lib/node_modules/node-gyp/lib/build.js:276:23)
gyp ERR! stack     at emitTwo (events.js:87:13)
gyp ERR! stack     at ChildProcess.emit (events.js:172:7)
gyp ERR! stack     at Process.ChildProcess._handle.onexit (internal/child_process.js:200:12)
gyp ERR! System Linux 4.4.0-57-generic
gyp ERR! command "/usr/bin/nodejs" "/usr/local/bin/node-gyp" "build"
gyp ERR! cwd /home/oleg/WebstormProjects/oresoftware/replace-line
gyp ERR! node -v v4.2.6
gyp ERR! node-gyp -v v3.4.0
gyp ERR! not ok 

I will try some of the the other examples, but would like to know how I can fix! thanks

Minimal example showing a persistent function callback stored as a class member?

Hey guys - I've been struggling to combine example 3 with example 6. In JavaScript, I'd like the usage to be something like:

var myObj = new MyObject(function() { console.log("hello world" });
myObj.doSomething(); // invoke the callback passed in the ctor

I've tried:

1. Creating a class member of type Persistent<Function>
2. Taking the Local<Function> from the ctor args list
3. Calling Reset() on the Persistent member to store a reference to the argument callback and keep it in scope
4. In doSomething() on the C++ side recreating the callback as a Local<Function>, e.g. New(isolate, this->myPersistent)

I'm having trouble with 4. I can't seem to figure out the correct way to rehydrate a callback from a Persistent in a way where it can actually be invoked. When trying 4, I receive what I assume is a seg fault as the node process immediately terminates. I must be doing something wrong but I can't find a snippet anywhere that demonstrates how to do this properly.

Any help would be greatly appreciated.

Nan 2 examples Readme

The examples were updated to nan 2 but the readme's still use the old syntax? I can change the readme but I think the content has to be rewritten in to those parts as they mean different things now.

How to use the v8 object type in cpp

I transfer the image buffer data from js to cpp, using Local value = args[0]->ToObject();
But after that I don't know how to use the data in cpp.
I hope to convert that to cv Mat type.
If someone know about it, please give me an advice.
Thank you.

unable get string length

I am now testing for echo function,

for code

napi_value Method(napi_env env, napi_callback_info args)
{
  // napi_value str;
  napi_status status;
  cout << "inside method!" << endl;

  size_t argc = 0;
  napi_value argv[1];
  status = napi_get_cb_info(env, args, &argc, argv, nullptr, nullptr);

  if (status != napi_ok)
  {
    napi_throw_error(env, NULL, "Error Get Parameters!");
    return nullptr;
  }
  cout << "before argc!" << endl;

  if (argc < 1)
  {
    cout << "" << endl;
    return nullptr;
  }
  size_t strlen;
  status = napi_get_value_string_utf8(env, argv[0], NULL, 0, &strlen);
  if (status != napi_ok)
  {
    napi_throw_error(env, NULL, "Error Get String Length!");

    return nullptr;
  }
  // status = napi_create_string_utf8(env, argv[0], NAPI_AUTO_LENGTH, res);
  // if (status != napi_ok)
  // {
  //   napi_throw_error(env, NULL, "Error Get String!");
  //   return nullptr;
  // }
  return nullptr;
}

and

  status = napi_set_named_property(env, exports, "echo", fn);

and

 echo('hello!')

,

I got:

inside method!
before argc!
before get string!
�"�d2
    1) hello


  0 passing (11ms)
  1 failing

  1) crypto
       hello:
     Error: Error Get String Length!
      at Context.it (tests/1-test.js:4:24)

Passing String containing null character in between.

I have a byte array of an image in nodejs and i want to pass it in a C function for further processing .
If i am passing it as string then the array is not passed correctly. Can you tell me how can i pass it?

Composition and Inheritance of Wrapped Objects Examples

Can examples of composition and inheritance of wrapped objects be added? I think one could potentially figure it out with the current examples, but I'm not able to figure it out.

class BasicClass { int IntValue; };
class BasicComposition
{
    int foo;
    BasicClass bc;
};
class BasicInheritance : BasicClass
{
    double yValue;
};
class InheritanceAndComposition : BasicInheritance
{
    std::string strValue;
    BasicComposition bcValue;
};

// Export all classes to JS

One should be able to instantiate and use each C++ class in JavaScript (e.g. create an instance of BasicClass independent of instances of BasicComposition).

It seems to me that only the case of BasicClass has an example in 6_object_wrap. The other cases with inheritance and composition of classes extending ObjectWrap<T> do not appear to exist. Inheritance might be covered in inherits_from_event_emitter, but it is not clear to me what is going on in that example.

I'm hoping someone with more experience with node-addon-api can provide these types of examples. It would greatly assist me in defining more complex relationships in Napi.

v0.11.13-pre and V8 3.25.30 refurbishing

Hi,

I upgraded all but 7_factory_wrap & 8_passing_wrapped. Get the

 Assertion `handle->InternalFieldCount() > 0' failed.

For the rest I can provide patch files. The changes are for V8 and node master branches as of today.

Working examples for Node v0.11.13?

I checked out 1_hello_world on the v0.11 branch, but the example doesn't compile (Windows 7, VS 2012).

Check out the following screenshot and error list:

Error   1 error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
Error   2 error C2143: syntax error : missing ',' before '&'
Error   3 error C2039: 'Close' : is not a member of 'v8::HandleScope'
Error   4 error C2039: 'New' : is not a member of 'v8::String'
Error   5 error C3861: 'New': identifier not found
Error   6 error C2039: 'NewSymbol' : is not a member of 'v8::String'
Error   7 error C2664: 'v8::FunctionTemplate::New' : cannot convert parameter 1 from 'v8::Handle<T> (__cdecl *)(const int)' to 'v8::Isolate *'  c:\users\mmaedler\documents\visual studio
Error   8 error C2227: left of '->GetFunction' must point to class/struct/union/generic type
Error   9 error C3861: 'NewSymbol': identifier not found

Is there anything I'm missing? The other examples for node-v0.10.31 did compile fine. All I could figure out is, that Arguments seems to be a member of the namespace v8::internals now.

P.S. It does indeed compile against node-v0.11.3. But I need my module to run with v0.11.13. Is this possible?

Thanks in advance

Callback example not working

Hi,
in example '3_callbacks\nan' is probably missing a return value in function 'RunCallback'.

Output of 'npm install':
e:\node_addons\node-addon-examples\3_callbacks\nan\addon.cc(14): error C4716: 'RunCallback' : must return a value [e:\node_addons\node-addon-examples\3_callbacks\nan\build\addon.vcxproj]
LINK : fatal error LNK1257: code generation failed [e:\node_addons\node-addon-examples\3_callbacks\nan\build\addon.vcxproj]

It can be fixed by adding a line:
return scope.Close(Undefined());

adding example for making a callback from another thread

Hi there! Maybe this is not really necessary. But I think I am kind of stuck in there. And it's really hard to find an example of this.

Just a suggestion :)

1_hello_world example => nody-gyp build failure

Recreating Issue #60

Issue was closed by reporter who cannot remember what the fix was.

Node v5.0.0
nan v2.0.0 & v2.7.0
[email protected]

gyp info spawn args [ 'BUILDTYPE=Release', '-C', 'build' ]
make: Entering directory '/home/peter/repos/node-struct/hello-world/build'
  CXX(target) Release/obj.target/hello/hello.o
../hello.cc: In function ‘Nan::NAN_METHOD_RETURN_TYPE Method(Nan::NAN_METHOD_ARGS_TYPE)’:
../hello.cc:6:12: error: ‘NanScope’ was not declared in this scope
   NanScope();
            ^
../hello.cc:7:18: error: ‘New’ is not a member of ‘v8::String’
   NanReturnValue(String::New("world"));
                  ^
../hello.cc:7:38: error: ‘NanReturnValue’ was not declared in this scope
   NanReturnValue(String::New("world"));
                                      ^
../hello.cc: In function ‘void Init(v8::Handle<v8::Object>)’:
../hello.cc:11:33: error: ‘NanSymbol’ was not declared in this scope
   exports->Set(NanSymbol("hello"), FunctionTemplate::New(Method)->GetFunction());
                                 ^
../hello.cc:11:64: error: no matching function for call to ‘v8::FunctionTemplate::New(Nan::NAN_METHOD_RETURN_TYPE (&)(Nan::NAN_METHOD_ARGS_TYPE))’
   exports->Set(NanSymbol("hello"), FunctionTemplate::New(Method)->GetFunction());
                                                                ^
In file included from /home/peter/.node-gyp/5.0.0/include/node/node.h:42:0,
                 from ../node_modules/nan/nan.h:49,
                 from ../hello.cc:1:
/home/peter/.node-gyp/5.0.0/include/node/v8.h:4348:34: note: candidate: static v8::Local<v8::FunctionTemplate> v8::FunctionTemplate::New(v8::Isolate*, v8::FunctionCallback, v8::Local<v8::Value>, v8::Local<v8::Signature>, int)
   static Local<FunctionTemplate> New(
                                  ^
/home/peter/.node-gyp/5.0.0/include/node/v8.h:4348:34: note:   no known conversion for argument 1 from ‘Nan::NAN_METHOD_RETURN_TYPE(Nan::NAN_METHOD_ARGS_TYPE) {aka void(const Nan::FunctionCallbackInfo<v8::Value>&)}’ to ‘v8::Isolate*’
hello.target.mk:96: recipe for target 'Release/obj.target/hello/hello.o' failed
make: *** [Release/obj.target/hello/hello.o] Error 1
make: Leaving directory '/home/peter/repos/node-struct/hello-world/build'
gyp ERR! build error 
gyp ERR! stack Error: `make` failed with exit code: 2
gyp ERR! stack     at ChildProcess.onExit (/home/peter/.nvm/v5.0.0/lib/node_modules/node-gyp/lib/build.js:258:23)
gyp ERR! stack     at emitTwo (events.js:87:13)
gyp ERR! stack     at ChildProcess.emit (events.js:172:7)
gyp ERR! stack     at Process.ChildProcess._handle.onexit (internal/child_process.js:200:12)
gyp ERR! System Linux 4.2.0-42-generic
gyp ERR! command "/home/peter/.nvm/v5.0.0/bin/node" "/home/peter/.nvm/v5.0.0/bin/node-gyp" "build"
gyp ERR! cwd /home/peter/repos/node-struct/hello-world
gyp ERR! node -v v5.0.0
gyp ERR! node-gyp -v v3.6.2
gyp ERR! not ok 

..\hello.cc(6): error C3861: 'NanScope': identifier not found

I have installed the latest nan. Is NanScope removed?

why async_work example was removed?

why async_work example was removed?

Update to 3.17.x API

I'm in the process of updating node to v8 3.17. This requires a few API changes to these examples. You can track the bug here: nodejs/node-v0.x-archive#5077

Don't have the commit up yet with the changes to api docs, but will soon.

Object wrap Init function

In the object wrap examples for node 0.12 there is no HandleScope in the Init function, but you use a Local handle. Is this a bug or on purpose? Great examples by the way, very instructive!

void MyObject::Init(Handle<Object> exports) {
  Isolate* isolate = Isolate::GetCurrent();

  // Prepare constructor template
  Local<FunctionTemplate> tpl = FunctionTemplate::New(isolate, New);

faile to build /5_function_factory/nan

  CXX(target) Debug/obj.target/addon/addon.o
In file included from ../addon.cc:1:0:
../node_modules/nan/nan.h:481:19: error: ‘NanNew’ declared as an ‘inline’ variable
       v8::String::ExternalAsciiStringResource *resource) {
                   ^
../node_modules/nan/nan.h:481:19: error: ‘v8::Local<v8::String> NanNew’ redeclared as different kind of symbol
../node_modules/nan/nan.h:475:36: error: previous declaration of ‘v8::Local<v8::String> NanNew(v8::String::ExternalStringResource*)’
   NAN_INLINE v8::Local<v8::String> NanNew(
                                    ^
../node_modules/nan/nan.h:481:7: error: ‘ExternalAsciiStringResource’ is not a member of ‘v8::String’
       v8::String::ExternalAsciiStringResource *resource) {
       ^
../node_modules/nan/nan.h:481:48: error: ‘resource’ was not declared in this scope
       v8::String::ExternalAsciiStringResource *resource) {
                                                ^
../node_modules/nan/nan.h: In function ‘bool _NanGetExternalParts(v8::Handle<v8::Value>, const char**, size_t*)’:
../node_modules/nan/nan.h:2103:12: error: ‘class v8::String’ has no member named ‘IsExternalAscii’
   if (str->IsExternalAscii()) {
            ^
../node_modules/nan/nan.h:2104:11: error: ‘ExternalAsciiStringResource’ in ‘class v8::String’ does not name a type
     const v8::String::ExternalAsciiStringResource* ext;
           ^
../node_modules/nan/nan.h:2105:5: error: ‘ext’ was not declared in this scope
     ext = str->GetExternalAsciiStringResource();
     ^
../node_modules/nan/nan.h:2105:16: error: ‘class v8::String’ has no member named ‘GetExternalAsciiStringResource’
     ext = str->GetExternalAsciiStringResource();
                ^
make: *** [Debug/obj.target/addon/addon.o] Error 1

build error on mac

I've have problem building node-gyp after the second example.
I'm working on mac Mavericks

 $4_object_factory git:(master) node-gyp rebuild   

gyp info it worked if it ends with ok
gyp info using [email protected]
gyp info using [email protected] | darwin | x64
gyp info spawn python
gyp info spawn args [ '/usr/local/lib/node_modules/node-gyp/gyp/gyp_main.py',
gyp info spawn args   'binding.gyp',
gyp info spawn args   '-f',
gyp info spawn args   'make',
gyp info spawn args   '-I',
gyp info spawn args   '/Users/lijung/Documents/school/node-addon-examples/4_object_factory/build/config.gypi',
gyp info spawn args   '-I',
gyp info spawn args   '/usr/local/lib/node_modules/node-gyp/addon.gypi',
gyp info spawn args   '-I',
gyp info spawn args   '/Users/lijung/.node-gyp/0.8.5/common.gypi',
gyp info spawn args   '-Dlibrary=shared_library',
gyp info spawn args   '-Dvisibility=default',
gyp info spawn args   '-Dnode_root_dir=/Users/lijung/.node-gyp/0.8.5',
gyp info spawn args   '-Dmodule_root_dir=/Users/lijung/Documents/school/node-addon-examples/4_object_factory',
gyp info spawn args   '--depth=.',
gyp info spawn args   '--generator-output',
gyp info spawn args   'build',
gyp info spawn args   '-Goutput_dir=.' ]
gyp info spawn make
gyp info spawn args [ 'BUILDTYPE=Release', '-C', 'build' ]
  CXX(target) Release/obj.target/addon/addon.o
../addon.cc:1:9: warning: 'BUILDING_NODE_EXTENSION' macro redefined
#define BUILDING_NODE_EXTENSION
        ^
<command line>:4:9: note: previous definition is here
#define BUILDING_NODE_EXTENSION 1
        ^
../addon.cc:20:20: error: cannot initialize a member subobject of type 'void (*)(v8::Handle<v8::Object>)' with an lvalue of type
      'void (Handle<v8::Object>, Handle<v8::Object>)': different number of parameters (1 vs 2)
NODE_MODULE(addon, Init)
                   ^~~~
/Users/lijung/.node-gyp/0.8.5/src/node.h:235:7: note: expanded from macro 'NODE_MODULE'
      regfunc,                                                        \
      ^
1 warning and 1 error generated.
make: *** [Release/obj.target/addon/addon.o] Error 1

Examples out of date

All of the Addon examples are out of date. We need v4, v5 and soon v6 examples. The most recent appear to be v0.12

Readme.md is out of date

NanScope(); for example does not compile

cannot compile Nan example 7 node v6 (latest)

Hello,
I was trying to compile example 7 with NAN but it fails and gives the following error:

(node) v8::ObjectTemplate::Set() with non-primitive values is deprecated
(node) and will stop working in the next major release.

Use NODE_GYP_MODULE_NAME in NAPI_MODULE and move files to .c if possible

Cross compiling errors

I've had success cross compiling modules, but I got the following error when trying to do so with the Hello World example code.

$ node hello.js 

module.js:356
  Module._extensions[extension](this, filename);
                               ^
Error: /node/addon/hello/build/Release/hello.node: wrong ELF class: ELFCLASS32
    at Module.load (module.js:356:32)
    at Function.Module._load (module.js:312:12)
    at Module.require (module.js:364:17)
    at require (module.js:380:17)
    at Object.<anonymous> (/node/addon/hello/hello.js:1:75)
    at Module._compile (module.js:456:26)
    at Object.Module._extensions..js (module.js:474:10)
    at Module.load (module.js:356:32)
    at Function.Module._load (module.js:312:12)
    at Function.Module.runMain (module.js:497:10)

I built with

$ node-gyp --arch arm rebuild
gyp info it worked if it ends with ok
gyp info using [email protected]
gyp info using [email protected] | linux | x64
gyp info spawn python
gyp info spawn args [ '/usr/local/lib/node_modules/node-gyp/gyp/gyp',
gyp info spawn args   'binding.gyp',
gyp info spawn args   '-f',
gyp info spawn args   'make',
gyp info spawn args   '-I',
gyp info spawn args   '/node/addon/hello/build/config.gypi',
gyp info spawn args   '-I',
gyp info spawn args   '/usr/local/lib/node_modules/node-gyp/addon.gypi',
gyp info spawn args   '-I',
gyp info spawn args   '/home/ubuntu/.node-gyp/0.10.0/common.gypi',
gyp info spawn args   '-Dlibrary=shared_library',
gyp info spawn args   '-Dvisibility=default',
gyp info spawn args   '-Dnode_root_dir=/home/ubuntu/.node-gyp/0.10.0',
gyp info spawn args   '-Dmodule_root_dir=/node/addon/hello',
gyp info spawn args   '--depth=.',
gyp info spawn args   '--generator-output',
gyp info spawn args   'build',
gyp info spawn args   '-Goutput_dir=.' ]
gyp info spawn make
gyp info spawn args [ 'BUILDTYPE=Release', '-C', 'build' ]
make: Entering directory `/node/addon/hello/build'
  CXX(target) Release/obj.target/hello/hello.o
  SOLINK_MODULE(target) Release/obj.target/hello.node
  COPY Release/hello.node
make: Leaving directory `/node/addon/hello/build'
gyp info ok 

To my eye, that looks ok. As a test, ran 'file' on the node binary:

file hello.node 
hello.node: ELF 32-bit LSB shared object, ARM, version 1 (SYSV), dynamically linked, not stripped

Which looks good.

Any suggestions?

Add async example to abi-stable-node-addon-examples

The example should also illustrate the use of napi_make_callback.

Re: nodejs/node#14256

Add property example

Can anyone add how to wrap properties on 6_object_wrap, I have tried Nan::SetAccessor，But it has 2 methods, and invoke the wrong function.

Thanks.

Keep this repo? Archive it?

@rvagg @eljefedelrodeodeljefe Is this repository something that should be maintained? Or archived? Seems to be pretty dormant.

Call Local<Function> with ObjectWrap as argument

I cannot find any information on how to create an ObjectWrap and pass it as an argument to a Local. I have a persistent callback registered and need to call it with a new instance of an ObjectWrap. I could do this by calling the (JS) constructor and pass it (JS) arguments which returns a new instance, but I want to avoid this round tripping.

Basically: how to create an ObjectWrap and get a Local out of it so that I can pass it as an argument to a JS function?

question about 6_object_wrap

I have a question about Persistent, in the sixth example

void MyObject::Init(Handle<Object> target) {
  // Prepare constructor template
  Local<FunctionTemplate> tpl = FunctionTemplate::New(New);
  tpl->SetClassName(String::NewSymbol("MyObject"));
  tpl->InstanceTemplate()->SetInternalFieldCount(1);
  // Prototype
  tpl->PrototypeTemplate()->Set(String::NewSymbol("plusOne"),
      FunctionTemplate::New(PlusOne)->GetFunction());

  Persistent<Function> constructor = Persistent<Function>::New(tpl->GetFunction());
  target->Set(String::NewSymbol("MyObject"), constructor);
}

why the constructor need to be defined as Persistent Handler instead of Local handler? I have tried to use Local and it also work.

Can you create example for async promise?

I'm trying to make async promise and I use AsyncWorker for it. But I think callback function is odd here
Do I do something wrong?

Napi::Value EmptyCallback(const Napi::CallbackInfo& info)
{
    Napi::Env env = info.Env();
    Napi::HandleScope scope(env);
    
    return env.Undefined();
}

class SumWorker : public Napi::AsyncWorker {
public:
    SumWorker(Napi::Function& callback, Napi::Promise::Deferred deferred, int num1, int num2)
    : Napi::AsyncWorker(callback), deferred(deferred), num1(num1), num2(num2), sum(0)) {}
    ~SumWorker() {}
    
    void Execute () {
        sum = num1 + num2;
    }

    void OnError() {
        Napi::HandleScope scope(Env());
       deferred.Reject(Napi::Error::New(Env(), "Something wrong"));
        
        // Call empty function
        Callback().Call({});
    }


    void OnOK() {
        Napi::HandleScope scope(Env());
        deferred.Resolve(Napi::Number::New(sum));
        
        // Call empty function
        Callback().Call({});
    }
    
private:
    Napi::Promise::Deferred deferred;
    int num1;
    int num2;
    int sum;
};

Napi::Value CallPromise(const Napi::CallbackInfo& info)
{
    Napi::Env env = info.Env();
    Napi::HandleScope scope(env);
    
    int num1 = info[0].As<Napi::Number>();
    int num2 = info[1].As<Napi::Number>();
    
    Napi::Promise::Deferred deferred = Napi::Promise::Deferred::New(info.Env());
    
    Napi::Function callback = Napi::Function::New(env, EmptyCallback);
    
    SumWorker* worker = new SumWorker(callback, deferred, num1, num2);
    worker->Queue();

    return deferred.Promise();
}

AsyncWorker question pertaining to Execute()

In the comments for the async_pi_estimate starting at line 11, there is a part that states "It is not safe to access JS engine data structure..."

• Is this referring to anything that uses info.Env() or does that mean something else?
• What limitations does that put on data that can be passed in and executed?
• Will I be able to pass a Napi::Buffer or would I have to convert it to a non-napi value before using it?

My use case is that I have a node-addon-api based addon that receives 2 pixel buffers and compares them for differences and then does labeling and blobbing. I will be adding more features to it that will most likely cause it to increase its time to process. My current implementation is synchronous/blocking and I am going to attempt to convert to async.

Any advice or guidance would be appreciated. Thanks.

JS Number conversion

https://github.com/rvagg/node-addon-examples/blob/master/9_async_work/async.cc#L68

Javascript numbers are represented using 64 bits, then isn't it better to just call to NumberValue() which returns a double or IntegerValue which returns int64_t?

http://bespin.cz/~ondras/html/classv8_1_1Value.html

[COMMENT] NAN 1.x support

with release of NAN 2.x, nodejs version must be >= 0.10.29, so i think it is beneficial to keep examples for both of the versions of nan, would you consider to put back nan_1.x alone with nan_2.x if I will make another pull request?

for example ubuntu trusty comes with 0.10.25
http://packages.ubuntu.com/search?keywords=nodejs&searchon=names&suite=trusty&section=all

Need example of napi_get_value_string_utf8

How to create utf8 string from a argument

wrap inherent

how to extend a wrap?

I know that there is
tpl->Inherit (parent)

but how to solve the question of unwarp, to get the correct object?
Dinamic?* w = ObjectWrap::Unwrap<Dinamic?>(args.This());

(sorry for my English)

every n-api have at lease one independent example

not just select one or two.

adding example for wrapping pre-created objects

Hey!
This is more like something I am stuck at.

I have a library with header files, and I want to make bindings for that library. Yet, I can not change the already existing classes. So, I am looking for a way to wrap these existing classes into a nodejs module.

Currently, I am waiting for some peeps to respond. But it would still be awesome if that would be added here, as it is quite a usual case.

Kind regards, Ingwie! ^^

echo example is need.

where

echo('abc')

will produce

abc