你也可以传递一个struct的函数，比如:

    package main
    // define struct
    type Apple struct {}
    
    // return apple's color
    func (Apple) GetColor() string {
         return "Red" 
    }
    
    func main () {
        // instantiate
        myApple := Apple{}
        
        // put the func in a variable
        theFunc := myApple.GetColor
        
        // execute the variable as a function
        color := theFunc()
    
        print(color)
    }

输出将为“红色”，检查操场

是的，Go确实接受一类函数。

请参阅文章“Go中的第一类函数”以获得有用的链接。

是的，考虑一下这些例子:

package main

import "fmt"

// convert types take an int and return a string value.
type convert func(int) string

// value implements convert, returning x as string.
func value(x int) string {
    return fmt.Sprintf("%v", x)
}

// quote123 passes 123 to convert func and returns quoted string.
func quote123(fn convert) string {
    return fmt.Sprintf("%q", fn(123))
}

func main() {
    var result string

    result = value(123)
    fmt.Println(result)
    // Output: 123

    result = quote123(value)
    fmt.Println(result)
    // Output: "123"

    result = quote123(func(x int) string { return fmt.Sprintf("%b", x) })
    fmt.Println(result)
    // Output: "1111011"

    foo := func(x int) string { return "foo" }
    result = quote123(foo)
    fmt.Println(result)
    // Output: "foo"

    _ = convert(foo) // confirm foo satisfies convert at runtime

    // fails due to argument type
    // _ = convert(func(x float64) string { return "" })
}

玩:http://play.golang.org/p/XNMtrDUDS0

参观:https://tour.golang.org/moretypes/25(函数闭包)

下面是Go中的“Map”实现示例。希望这能有所帮助!!

func square(num int) int {
    return num * num
}

func mapper(f func(int) int, alist []int) []int {
    var a = make([]int, len(alist), len(alist))
    for index, val := range alist {

        a[index] = f(val)
    }
    return a
}

func main() {
    alist := []int{4, 5, 6, 7}
    result := mapper(square, alist)
    fmt.Println(result)

}

这里有一个简单的例子:

    package main

    import "fmt"

    func plusTwo() (func(v int) (int)) {
        return func(v int) (int) {
            return v+2
        }
    }

    func plusX(x int) (func(v int) (int)) {
       return func(v int) (int) {
           return v+x
       }
    }

    func main() {
        p := plusTwo()
        fmt.Printf("3+2: %d\n", p(3))

        px := plusX(3)
        fmt.Printf("3+3: %d\n", px(3))
    }

你可以把函数作为参数传递给Go函数。下面是一个将函数作为参数传递给另一个Go函数的例子:

package main

import "fmt"

type fn func(int) 

func myfn1(i int) {
    fmt.Printf("\ni is %v", i)
}
func myfn2(i int) {
    fmt.Printf("\ni is %v", i)
}
func test(f fn, val int) {
    f(val)
}
func main() {
    test(myfn1, 123)
    test(myfn2, 321)
}

你可以在https://play.golang.org/p/9mAOUWGp0k上尝试一下