reflect.MakeFunc去.如何返回一个err=nil作为reflect.Value

Question

如何返回err=nil作为reflect.Value?我需要写一个与reflect.MakeFunc()一起使用的交换函数。

//my swap implementation, that call the original function and cache results
func swapFunc(ins []reflect.Value) []reflect.Value {
    //After cache the first return (Offer) of function FindBestOffer(int)(Offer,bool,error),
    //i need to return the best Offer cached and default values 
    //for the two other returns (bool=true, err=nil)
    outs := make([]reflect.Value, 3) //mock cache return
    outs[0] = reflect.ValueOf(Offer{10, "cached offer", 20})
    outs[1] = reflect.ValueOf(true)
    outs[2] = reflect.ValueOf(nil).Elem() // --> Doesn't work!
    return outs
}

Go Playground完整示例

Answer 1

定义一个类型为nil的错误也可以…

var err error = nil
outs[2] = reflect.ValueOf(&err).Elem()

只是出于好奇。去操场上

Answer 2

这很棘手，你必须使用reflect.Zero:

out[2] = reflect.Zero(reflect.TypeOf((*error)(nil)).Elem())