dongyong2906
2014-07-02 17:34
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已采纳

Reflect.Value.FieldByName导致恐慌

I'm getting the following error when calling the .FieldByName method of a reflected value, the exact error is :-

panic: reflect: call of reflect.Value.FieldByName on ptr Value

and the code is :-

s := reflect.ValueOf(&value).Elem() (value is a struct)
metric := s.FieldByName(subval.Metric).Interface() (subval.Metric is a string)

I understand this isn't much, but this is all the information I can get.

Here's a link to the code on Go Playground: http://play.golang.org/p/E038cPOoGp

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2条回答 默认 最新

  • duanqun9740 2014-07-02 18:01
    已采纳

    Your value is already a pointer to a struct. Try printing out s.Kind() in your code.

    There's no reason to take the address of value, then call Elem() on that reflect.Value, which dereferences the pointer you just created.

    s := reflect.ValueOf(value).Elem()
    metric := s.FieldByName(subvalMetric).Interface()
    fmt.Println(metric)
    
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  • dpfw3607 2014-07-02 18:06

    If you add few println you understand what happens:

    http://play.golang.org/p/-kaz105_En

    for _, Value:= range NewMap {
        s := reflect.ValueOf(&Value).Elem()
        println(s.String())
        println(s.Elem().String())
        metric := s.Elem().FieldByName(subvalMetric).Interface()
        fmt.Println(metric)
    }
    

    Output:

    <*main.Struct1 Value>
    <main.Struct1 Value>
    abc
    
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