dongtaotao19830418
dongtaotao19830418
2016-05-23 07:00

带有特殊前缀/后缀的调用函数

已采纳

I have a package named "seeder":

package seeder

import "fmt"

func MyFunc1() {
    fmt.Println("I am Masood")
}

func MyFunc2() {
    fmt.Println("I am a programmer")
}

func MyFunc3() {
    fmt.Println("I want to buy a car")
}

Now I want to call all functions with MyFunc prefix

package main

import "./seeder"

func main() {
    for k := 1; k <= 3; k++ {
        seeder.MyFunc1() // This calls MyFunc1 three times
    }
}

I want something like this:

for k := 1; k <= 3; k++ {
    seeder.MyFunc + k ()
}

and this output:

I am Masood
I am a programmer
I want to buy a car

EDIT1: In this example, parentKey is a string variable which changed in a loop

for parentKey, _ := range uRLSjson{ 
    pppp := seeder + "." + strings.ToUpper(parentKey)
    gorilla.HandleFunc("/", pppp).Name(parentKey)
}

But GC said:

use of package seeder without selector

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2条回答

  • dqbhdsec59405 dqbhdsec59405 5年前

    You can't get a function by its name, and that is what you're trying to do. The reason is that if the Go tool can detect that a function is not referred to explicitly (and thus unreachable), it may not even get compiled into the executable binary. For details see Splitting client/server code.

    With a function registry

    One way to do what you want is to build a "function registry" prior to calling them:

    registry := map[string]func(){
        "MyFunc1": MyFunc1,
        "MyFunc2": MyFunc2,
        "MyFunc3": MyFunc3,
    }
    for k := 1; k <= 3; k++ {
        registry[fmt.Sprintf("MyFunc%d", k)]()
    }
    

    Output (try it on the Go Playground):

    Hello MyFunc1
    Hello MyFunc2
    Hello MyFunc3
    

    Manual "routing"

    Similar to the registry is inspecting the name and manually routing to the function, for example:

    func callByName(name string) {
        switch name {
        case "MyFunc1":
            MyFunc1()
        case "MyFunc2":
            MyFunc2()
        case "MyFunc3":
            MyFunc3()
        default:
            panic("Unknown function name")
        }
    }
    

    Using it:

    for k := 1; k <= 3; k++ {
        callByName(fmt.Sprintf("MyFunc%d", k))
    }
    

    Try this on the Go Playground.

    Note: It's up to you if you want to call the function identified by its name in the callByName() helper function, or you may choose to return a function value (of type func()) and have it called in the caller's place.

    Transforming functions to methods

    Also note that if your functions would actually be methods of some type, you could do it without a registry. Using reflection, you can get a method by name: Value.MethodByName(). You can also get / enumerate all methods without knowing their names using Value.NumMethod() and Value.Method() (also see Type.NumMethod() and Type.Method() if you need the name of the method or its parameter types).

    This is how it could be done:

    type MyType int
    
    func (m MyType) MyFunc1() {
        fmt.Println("Hello MyFunc1")
    }
    
    func (m MyType) MyFunc2() {
        fmt.Println("Hello MyFunc2")
    }
    
    func (m MyType) MyFunc3() {
        fmt.Println("Hello MyFunc3")
    }
    
    func main() {
        v := reflect.ValueOf(MyType(0))
        for k := 1; k <= 3; k++ {
            v.MethodByName(fmt.Sprintf("MyFunc%d", k)).Call(nil)
        }
    }
    

    Output is the same. Try it on the Go Playground.

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  • dsj60862 dsj60862 3年前

    Another alternative would be to range over an array of your functions

    package main
    
    import (
        "fmt"
    )
    
    func MyFunc1() {
        fmt.Println("I am Masood")
    }
    
    func MyFunc2() {
        fmt.Println("I am a programmer")
    }
    
    func MyFunc3() {
        fmt.Println("I want to buy a car")
    }
    
    
    func main() {
       for _, fn := range []func(){MyFunc1, MyFunc2, MyFunc3} {
            fn()
        }
    }
    
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