在Go中编写更简洁的代码

Question

I'm writing a package with functions which read data from XML-RPC server and store it in arrays of go structs. Here is the snippet just for two kinds of structs: http://play.golang.org/p/a1dVA0UCzS. For each type of struct I have a separate "conversion" function. There are more than 20 of them in total - just plain copies of each other with just struct names replaced.

Is there an elegant solution instead of stupid copy/paste of the same code?

Answer 1

You can do this by using reflection. See the pkg/reflect documentation.

For your case reflect.MakeFunc is interesting. You can create functions using reflection which then send a message and know the types they will receive. Example usage:

var getFooRequest func() []Foo                      // Prototype of request.
buildRequest("FooStore.GetFoo", &getFooRequest)     // Build request function.

result := getFooRequest()                           // Actually sending.

A working example (play):

func makeRequestFunc(req string, fptr interface{}) {
    baseRequestFunc := func(params []reflect.Value) []reflect.Value {
        log.Println("Sending", req)
        return []reflect.Value{ reflect.ValueOf([]int{1,2,3,4}) }
    }

    fn := reflect.ValueOf(fptr).Elem()
    reqFun := reflect.MakeFunc(fn.Type(), baseRequestFunc)
    fn.Set(reqFun)
}

var fooRequest func() []int

makeRequestFunc("foo", &fooRequest)

log.Println( fooRequest() )

baseRequestFunc in this example is the place where you would call your store.client.Call with whatever string you like. From this base function you create a new function that is callable using reflect.MakeFunc and store the result in the passed function pointer.

As fooRequest has a definite signature, no value unpacking is needed.