Golang与接收器的功能图

Question

Is there anyway to make a map of function pointers, but functions that take recievers? I know how to do it with regular functions:

package main

func someFunc(x int) int {
    return x
}

func main() {
    m := make(map[string]func(int)int, 0)
    m["1"] = someFunc
    print(m["1"](56))
}

But can you do that with functions that take recievers? Something like this (though I've tried this and it doesn't work):

package main

type someStruct struct {
    x int
}

func (s someStruct) someFunc() int {
    return s.x
}

func main() {
    m := make(map[string](someStruct)func()int, 0)
    s := someStruct{56}
    m["1"] = someFunc
    print(s.m["1"]())
}

An obvious work around is to just pass the struct as a parameter, but that's a little dirtier than I would have liked

Answer 1

You can do that using Method Expressions:

https://golang.org/ref/spec#Method_expressions

The call is a bit different, since the method expression takes the receiver as the first argument.

Here's your example modified:

package main

type someStruct struct {
    x int
}

func (s someStruct) someFunc() int {
    return s.x
}

func main() {
    m := make(map[string]func(someStruct)int, 0)
    s := someStruct{56}
    m["1"] = (someStruct).someFunc
    print(m["1"](s))
}

And here's a Go playground for you to test it:

https://play.golang.org/p/PLi5A9of-U