Declaring map with function pointer value in goLang

Question

I'd like to declare a map that would that would look like this, so I could map various init functions to initType :

func makeMap(){

    m := make(map[initType]&InitFunc)
    //How should the value declaration be set up for this map?

}


type initType int 

const(
    A initType = iota
    B
    C
    D
)


func init(aInitType initType){
    doStuff(aInitType)

}


func init(aInitType initType){
    doOtherStuff(aInitType)

}


func init(aInitType initType){
    doMoreStuff(aInitType)

}

How do I declare the function pointer type (which I called &InitFunc in the example because I don't know how to do it) so I can use it as the value in a Map?

Answer 1

Unlike C, you don't actually need a "pointer" to the function, since in Go, functions are reference types, similar to slices, maps, and channels. Further, the address operator, &, produces a pointer to a value, but to declare a pointer type, use *.

You seem to be wanting your InitFunc to take a single InitType and return no values. In that case, you would declare it as:

type InitFunc func(initType)

Now, your map initialization can simply look like:

m := make(map[initType]InitFunc)

A complete example would be ( http://play.golang.org/p/tbOHM3GKeC ):

package main

import "fmt"

type InitFunc func(initType)
type initType int

const (
    A initType = iota
    B
    C
    D
    MaxInitType
)

func Init1(t initType) {
    fmt.Println("Init1 called with type", t)
}

var initFuncs = map[initType]InitFunc{
    A: Init1,
}

func init() {
    for t := A; t < MaxInitType; t++ {
        f, ok := initFuncs[t]
        if ok {
            f(t)
        } else {
            fmt.Println("No function defined for type", t)
        }
    }
}

func main() {
    fmt.Println("main called")
}

Here, it's looping through each initType, and calling the applicable function, if it is defined.