The degorator from starwander

degorator's Introduction

Decorator in Golang

Degorator implements the decorator pattern in Golang. This can be used to add behavior, such as logs or metrics, into a function without affecting the original behavior at runtime.

##Requirements

go get github.com/starwander/degorator

Usage

Decorate: injects two functions(injectedBefore & injectedAfter) into the target function.
MakeDecorator: generate a decorator to a certain function type which can be used later.

Original	Decorated
func Myfunc(in)out{	func MyfuncDecorated(in)out{
......	injectedBefore(in)
do someting	out = MyFunc(in)
......	injectedAfter(out,in)
}	}

Example

package main

import (
	"fmt"
	"github.com/starwander/degorator"
)

type Counter struct {
	number int
	error  int
}

func (m *Counter) add(s string) {
	if s == "nothing" {
		return
	}
	m.number++
}

func (m *Counter) addErr(err error) {
	if err != nil {
		m.error++
	}
}

func Log(s string) {
	fmt.Println("input:", s)
}

type MyFunc func(s string) error

var myFunc MyFunc = func(s string) error {
	if s == "error" {
		return fmt.Errorf("error")
	}
	return nil
}

func main() {
	counter := new(Counter)

	var CounterDecorator func(MyFunc) MyFunc
	err := degorator.MakeDecorator(&CounterDecorator, counter.add, counter.addErr)
	if err != nil {
		panic(err)
	}
	myFunc = CounterDecorator(myFunc)

	myFunc("something")
	//1 0
	fmt.Println(counter.number, counter.error)

	myFunc("error")
	//2 1
	fmt.Println(counter.number, counter.error)

	myFunc("nothing")
	//2 1
	fmt.Println(counter.number, counter.error)

	var myFuncDecorated MyFunc
	err = degorator.Decorate(&myFuncDecorated, myFunc, Log, nil)
	if err != nil {
		panic(err)
	}

	//input: another
	myFuncDecorated("another")
	//3 1
	fmt.Println(counter.number, counter.error)
}