How Can I Create Function Wrappers in Go to Inject Code Before and After Function Execution?

Function Wrapper in Go

In Go, it is possible to create a function wrapper that takes a function as input and returns a wrapped version of it. This allows for injecting code before and after the execution of the wrapped function.

To define a function wrapper, you must specify the signature of the function you want to wrap. Here's an example:

func funcWrapper(myFunc interface{}) {
    fmt.Println("Before")
    //call myFunc
    fmt.Println("After")
}

In this example, the function wrapper takes a variable of type interface{} as input, which allows it to accept functions of different signatures. When the wrapped function is called, the code before and after the function call is executed.

However, this approach requires you to specify the signature of the function you want to wrap. A more flexible solution is to use a function literal that can accept functions of any signature:

func wrap(f func(i int) int) func(i int) int {
    return func(i int) (ret int) {
        fmt.Println("Before, i =", i)
        ret = f(i)
        fmt.Println("After, ret =", ret)
        return
    }
}

This wrapper function takes a function that takes an int as input and returns an int. It then returns a new function that executes the code before and after the wrapped function is called.

To use the wrapper, you pass the function you want to wrap as an argument:

wf := wrap(myfunc)
ret := wf(2)
fmt.Println("Returned:", ret)

This example wraps the myfunc function and prints the input and return values of the wrapped function.

In Go, you can create separate wrapper functions for different function types to ensure type safety and ease of use.

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