download12749 2018-05-18 14:30
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类型reflect.Value不支持索引

I have an array of generic type interface{} and I would to check if that array contains a certain value in one of its JSON object.

 history := reflect.ValueOf(historyInterface)
        for i := 0; i < history.Len(); i++ {
            // here I can get a map object
            test := history.Index(i) 
            // then I tried to access the id property of the object 
            // but here it fails
            fmt.Println("test", test["id"].(string)) 
        }

Below is what test will look like for each iteration:

first iteration
map[id:5afbff19bf07c79c19ed9af9 date:Saturday, January 21, 2017 9:21 PM certitude:33]
second iteration
map[id:afbff198658487a3e3e376b date:Thursday, March 3, 2016 2:24 PM certitude:30]

invalid operation: test["id"] (type reflect.Valuedoes not support indexing)

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1条回答 默认 最新

  • dshkmamau65777662 2018-05-18 15:48
    关注

    If historyInterface is created by unmarshaling JSON to an interface{}, then the map has type map[string]interface{}. Use a type assertion to get the map as that type:

     history := reflect.ValueOf(historyInterface)
     for i := 0; i < history.Len(); i++ {
        test := history.Index(i).Interface().(map[string]interface{})
        fmt.Println("test", test["id"].(string)) 
     }
    

    Also based on the assumption on the source of data, the application can use type assertions instead of reflect.

     history := historyInterface.([]interface{})
     for _, m := range history {
         test := m.(map[string]interface{})
         fmt.Println("test", test["id"].(string)) 
     }
    
    本回答被题主选为最佳回答 , 对您是否有帮助呢?
    评论

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