golang 断言：一个蛋疼的处理场景

这一切都来源于一个蛋疼的需求场景处理：

因为历史原因，一个需要用到的 JSON 数据被整个缓存进 Redis 的一个 key 中，大概如下：

127.0.0.1:6379> get dt
"{\"address\":[{\"duration\":90,\"format\":\"mp4\",\"url\":\"xxx.mp4\",\"ext\":\"{\\\"key\\\":\\\"val\\\"}\"},{\"duration\":90,\"format\":\"mp4\",\"url\":\"xxx.mp4\",\"ext\":\"{\\\"key\\\":\\\"val\\\"}\"}],\"value\":\"web\"}"
127.0.0.1:6379>
​

这里还是做了脱敏处理，实际的情形 JSON 的层级更深...
格式化显示的 JSON 结构大概是这样：

{
    "address": [
        {
            "duration": 90,
            "format": "mp4",
            "url": "xxx.mp4",
            "ext": "{\"key\":\"val\"}"
        },
        {
            "duration": 90,
            "format": "mp4",
            "url": "xxx.mp4",
            "ext": "{\"key\":\"val\"}"
        }
    ],
    "value": "web"
}
​

现在要做的是： address 里的每个元素的 url 字段需要更新。

现在知道的是：address 的值 是一个数组，数组的每个元素是一个 map[string]interface{} 类型，map 里的元素除了 "url": "xxx.mp4" , 其他的数量不确定

实现代码大概如下（方便展示，省略了 Redis 读写的步骤）：

	detailByte := []byte(`{"address":[{"duration":90,"format":"mp4","url":"xxx.mp4","ext":"{\"key\":\"val\"}"},{"duration":90,"format":"mp4","url":"xxx.mp4","ext":"{\"key\":\"val\"}"}],"value":"web"}`)
	detail := make(map[string]interface{}, 0)
	json.Unmarshal(detailByte, &detail)
	formatJson, _ := json.MarshalIndent(detail, "", "    ")
	fmt.Println("before: ", string(formatJson))
	if address, ok := detail["address"]; ok {
		if item, ok2 := address.([]interface{}); ok2 {
			for index, value := range item {
				if vMap, ok3 := value.(map[string]interface{}); ok3 {
					if _, ok4 := vMap["url"]; ok4 {
						vMap["url"] = "wtf.mp4"
					}
					item[index] = vMap
				}
			}
			detail["address"] = item
		}
	}
	formatJson, _ = json.MarshalIndent(detail, "", "    ")
	fmt.Println("after: ", string(formatJson))
​

运行结果：

before:  {
    "address": [
        {
            "duration": 90,
            "ext": "{\"key\":\"val\"}",
            "format": "mp4",
            "url": "xxx.mp4"
        },
        {
            "duration": 90,
            "ext": "{\"key\":\"val\"}",
            "format": "mp4",
            "url": "xxx.mp4"
        }
    ],
    "value": "web"
}
after:  {
    "address": [
        {
            "duration": 90,
            "ext": "{\"key\":\"val\"}",
            "format": "mp4",
            "url": "wtf.mp4"
        },
        {
            "duration": 90,
            "ext": "{\"key\":\"val\"}",
            "format": "mp4",
            "url": "wtf.mp4"
        }
    ],
    "value": "web"
}
​

怎么说呢，实现了感觉又没有真正实现...

哎，蛋疼。