There are two reasons you might want to stream data instead of loading it all and then parsing the complete set - (a) low memory usage and (b) speed to first item.
In my case it was speed to first item - I had a problem where there was a large dataset that came down slowly so I wanted a way to display the first few items while the rest were still arriving.
My other condition was that I didn't want to modify AFNetowrking to get this to work :)
There's an example in the Example folder - open and run Demo.xcworkspace and it should show a list of names. Very exciting.
Take a look at the only view controller in the app and it should become more interesting :| It reads in an array of JSON (see example.json in the project) and parses it as it arrives (using SBJson's stream parsing).
Basically, use DWHTTPStreamSessionManager instead of AFHTTPSessionManager - it's a direct subclass so everything will work as normal. The only changes are the addition of the GET:parameters:data:success:failure method. This performs exactly the same request as the usual GET method but instead of returning the parsed data in it's success block it returns each chunk as it arrives.
The default implementation of this class just returns each chunk of data (as NSData) to the chunk callback block. If you want this to automagically be parsed, you can provide a better itemSerializer - an example implementation of this is in the Json subpod - this implements the DWHTTPJSONItemSerializerProvider which will use SBJson4 to parse an input stream like
[
{ "name":"Alice" },
{ "name":"Bob" },
{ "name":"Carl" },
...
]
passing each dictionary as an item to the chunk callback block. This method is used in the example project (in the Example folder) - check it out :)
## TODO
This isn't as efficient as it could be because of the 'don't modify AFNetworking' constraint. DWHTTPStreamSessionManager doesn't allow AFNetworking to build up the entire data set but AFNetworking doesn't know that so it still tries to serialize the response and pass it back to the success block. It's a tiny inefficiency and is hidden from you by DWHTTPStreamSessionManager. I couldn't find a way to remove it without modifying AFNetworking :(
AFNetworking+streaming is available through CocoaPods. To install it, simply add the following line to your Podfile:
pod "AFNetworking+streaming"
What if you don't want to have SBJson as a dependency? i.e. you might be parsing an XML stream or you might just not like SBJson ;) That's easy, just require the Core subpod instead of everything. SBJson is only a dependency of the JSON item serialiser subpod :)
Sam Dean, [email protected]
AFNetworking+streaming is available under the MIT license. See the LICENSE file for more info.
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