Go-Type

在谈论struct和interface已经用到了type这个关键字。

另外，Go的type另外一种常用功能，是类似于C/C++的typedef。在Go的package中，这种用法非常常见。

A type declaration defines a new named type that has the same underlying type as an existing type. The named type provides a way to separate different and perhaps incompatible uses of the underlying type so that they can’t be mixed unintentionally.

type name underlying-type

示例：

package main 

import (
    "fmt"
)

type Hello interface {
    out()
}

type MyInt int 

func (myInt *MyInt) out() {
    fmt.Println("MyInt.out():", *myInt)
}

func foo(i MyInt) {
    fmt.Println("foo():", i)
}

func main() {
    var i MyInt 
    i = 5 
    i.out() //MyInt.out(): 5
    foo(i) // foo(): 5
    foo(1) // foo(): 1

    var x int 
    x = 100 
    //foo(x) //cannot use x (type int) as type MyInt in argument to foo
    foo(MyInt(x)) // foo(): 100
}

注：foo(MyInt(x)) 给出了Go中强制类型转换的使用示例。——和C/C++的类型转换语法刚好相反（e.g. foo((MyInt)x)）。