Wrapper for arbitrary function in Go

Issue

Is it possible to create a wrapper for arbitrary function in Go that would take the same arguments and return the same value?

I’m not talking about the wrapper that would look exactly the same, it may look differently, but it should solve the problem.

For example the problem might be to create a wrapper of arbitrary function that first looks for the result of the function call in cache and only in case of cache miss executes the wrapped function.

Solution

The answer based on @joshlf13 idea and answer, but seems more simple to me.
http://play.golang.org/p/v3zdMGfKy9

package main

import (
    "fmt"
    "reflect"
)

type (
    // Type of function being wrapped
    sumFuncT func(int, int) (int)

    // Type of the wrapper function
    wrappedSumFuncT func(sumFuncT, int, int) (int)
)

// Wrapper of any function
// First element of array is the function being wrapped
// Other elements are arguments to the function
func genericWrapper(in []reflect.Value) []reflect.Value {
    // this is the place to do something useful in the wrapper
    return in[0].Call(in[1:])
}

// Creates wrapper function and sets it to the passed pointer to function
func createWrapperFunction(function interface {}) {
    fn := reflect.ValueOf(function).Elem()
    v := reflect.MakeFunc(reflect.TypeOf(function).Elem(), genericWrapper)
    fn.Set(v)
}

func main() {
    var wrappedSumFunc wrappedSumFuncT

    createWrapperFunction(&wrappedSumFunc)

    // The function being wrapped itself
    sumFunc := func (a int, b int) int {
        return a + b
    }

    result := wrappedSumFunc(sumFunc, 1, 3)
    fmt.Printf("Result is %v", result)
}

Answered By – Alexander Ponomarev

Answer Checked By – Candace Johnson (GoLangFix Volunteer)

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