在Go中用类型声明替换包装结构

Question

I want to extend the regexp from the Go standard library to be able to define my own methods. I use the following struct:

type RichRegexp struct {
    *regexp.Regexp
}

As you can see, this struct contains nothing but the wrapped regexp.Regexp. So I wonder whether I could replace this with a simple type declaration like this:

type RichRegexp regexp.Regexp

But how should I write the following func then?

func Compile(expression string) (*RichRegexp, error) {
    regex, err := regexp.Compile(expression)
    if err != nil {
        return nil, err
    }
    return &RichRegexp{regex}, nil // How to do this?
}

I tried to convert regexp.Regexp to my RichRegexp but it didn't compile. What is the general pattern to return a custom type which wraps a underlying type?

Answer 1

package main

import (
        "regexp"
)

type RichRegexp regexp.Regexp

func Compile(expression string) (*RichRegexp, error) {
        regex, err := regexp.Compile(expression)
        if err != nil {
                return nil, err
        }

        return (*RichRegexp)(regex), nil
}

func main() {
    Compile("foo")
}

Also here: http://play.golang.org/p/cgpi8z2CfF