kapilgupta101292 / learngo

Learn Go

This is a ReadMe template to learn basic syntax of Golang.

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Table of Contents

You're sections headers will be used to reference location of destination.

• Description
• How To Use
• Basic Syntax
• Error Handling
• Struct in Go
• Pointers in Go
• Interface in Go
• Go Routines
• References
• License
• Author Info

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Description

Creating ReadMe's for your Github repository can be tedious. I hope this template can save you time and effort as well as provide you with some consistency across your projects.

Technologies

• Technology 1
• Technology 2

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How To Use

Basic Syntax

1. string(bs) -> converts Byte Slice to the String type

2. strings.split(s, separator string) -> String.split(String s,char c)

3. rand.Intn(i int) -> Random.rand(Integer i)

4. fmt.Printf("%+v", struct) -> Prints the value of each field in the struct followed by actual value

5. Value Types -> int, float, string, bool, structs (we use pointers to change these things in a function)

6. Reference Types -> slice, maps, channels, pointers, functions. Don't worry about pointers with these.

7. Make Function -> bs = make([] byte, 9999) - makes a byte slice with 9999 elements in it.

8. io.Copy -> io.Copy(os.Stdout, resp.Body)

Installation

API Reference

    <p>dummy code</p>

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References

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Error Handling

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Unit Tet in Go

Unit Test in Go

• To make a test, create a new file ending in _test.go like deck_test.go
• To run all the tests in a package, run the command

    go test

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Struct in Go

• Data Structure, Collection of properties that are related.
• Declaring a struct

type person struct {
    firstName string
    lastName string
}

func main() {
    alex := person{firstName: Alex, lastName: Anderson}
    fmt.Println(alex)
}

More Example of Struct

type contactInfo struct {
	email   string
	zipCode int
}

type person struct {
	firstName string
	lastName  string
	contactInfo
}

func main() {
	jim := person{
		firstName: "Jim",
		lastName:  "Party",
		contactInfo: contactInfo{
			email:   "[email protected]",
			zipCode: 94000,
		},
	}
	fmt.Printf("%+v", jim)
}

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Pointers in Go

• &variable -> (& is an operator) Give me the memory address of the value this variable is pointing at.
• *pointer -> (* is an operator) Give me the value that this memory addresss is pointing to.
• *person -> (person is a struct type) Type description - we are working with a pointer to a person.

Turn address into value using *address.
Turn value into adderss using &value.
Pointer shortcut is to call a function expecting the pointer to a type using the type only.

    func (pointerToPerson *person) updateName() {
        (*pointerToPerson).firstname = "jimmy"
    }

Pointer Gotcha

The below code will output [Bye There How Are You] which is different than expectation, but behaviour of Pointers is different for slice and struct.

    func main() {
        mySlice := []string{"Hi", "There", "How", "Are", "You"}
        updateSlice(mySlice)
        fmt.Println(mySlice)
    }

    func updateSlice(s []string) {
        s[0] = "Bye"
    }

Slice internally stores the elements in an array. Slice has three components (ptr to head of an array, capacity, length). Hence even when there is a copy of slice the underlying array is the same.

slice is referred to as Reference type.

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Map in Go

Map stores key, value pairs, all keys and all values should be of same type respectively

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Interface in Go

Declaring an interface type in a file, says our program has a new type called bot

    type bot interface {
	getGreeting() string
}
type englishBot struct{}
type spanishBot struct{}

func main() {
	eb := englishBot{}
	sb := spanishBot{}

	printGreeting(eb)
	printGreeting(sb)
}

func printGreeting(b bot) {
	fmt.Println(b.getGreeting())
}
func (englishBot) getGreeting() string {
	return "Hi There!"
}

func (spanishBot) getGreeting() string {
	return "Hola!"
}

If you are a type in this program with a function called 'getGreeting' and you return a string then you are a member of type 'bot'

Now that you are an honorary member of type 'bot' you can now call this function called printGreeting()

• Interfaces are not generic types and Go does not have support for the same.
• Interfaces are implicit, as in java we don't manually have to say that our custom type satisfies some interface
• Interfaces are a contract to help us manage types. if our custom type implementation is broken interfaces won't help.
• Interfaces are tough. Step #1 is understanding to read them. Writing our own interfaces is tough and requires experience.
• We can take different interfaces and combine them together to form a new interface.

    type ReadCloser interface {
        Reader 
        Closer
    }

    type Reader interface {
        read([]byte) (int, error)
    }

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Go Routines

1. Our running program (a process) --

Author Info

• Github - Kapil Gupta

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