My Go practice code

Go Lang notes

1. Basic syntax
2. Concurrency

Some special feature in Go

Defer
A defer statement will hold until surrounding function finish executing.

Function literal

A function literal represents a anonymous function.

Function closure

They may refer to variables defined in an enclosing function. Such variables :

1. are shared between the surrounding function and function literal
2. and survived as long as they are accessible

// NewCounter returns a function Count.
// Count prints the number of times it has been invoked.
func NewCounter() (Count func()) {
	n := 0
	return func() {
		n++
		fmt.Println(n)
	}
}

func main() {
	counter := NewCounter()
	otherCounter := NewCounter()

	counter()      // 1
	counter()      // 2
	counter()      // 3
	otherCounter() // 1 (different n)
	otherCounter() // 2
	counter()      // 4
}

Fibonacci generator using function closure.
Reference : https://www.calhoun.io/5-useful-ways-to-use-closures-in-go/

Function Receiver

No matter the receiver receive value or pointer, both value and pointer can use it. We prefer receiver type is pointer due to some reasons:

1. The method can modify the value that its receiver points to.
2. Avoid copying the value on each method call. This can be more efficient if the receiver is a large struct.

Interface

It is like a top level representation, different type implement it, as the interface's initialization.

Defer

Three rules :

1. A deferred function's arguments are evaluated when the defer statement is evaluated. The deferred call will print 0.

func a() {
    i := 0
    defer fmt.Println(i)
    i++
    return
}

2. Deferred function calls are executed in Last In First Out order after the surrounding function returns. It will print 3210.

func b() {
    for i := 0; i < 4; i++ {
        defer fmt.Print(i)
    }
}

3. Deferred functions may read and assign to the returning function's named return values.

Why the declaration is different from C ?

Go believe their declaration style makes the complex declaration more readible.

Projects

1. A simple server example

Reference

1. A tour of Go
2. Slice and Array
3. Go中文筆記
4. Defer