英文:
how to append string to the map of string to interface type
问题
我有一个创建的字符串到interface{}的映射。
x := make(map[string]interface{})
最终我需要以下输出。
x["key1"] = ["value1","value2","value3", ......]
有人可以帮忙吗？如何将字符串值追加到这个映射中？
英文:
I have a map of string to interface{} created
x := make(map[string]interface{})
ultimately i need the following output
x["key1"] = ["value1","value2","value3", ......]
can anyone help , how to append string values to this map ?
答案1
得分: 4
你只能向切片（slices）追加元素，而不能向映射（maps）追加元素。
要添加你列出的值，请使用以下代码：
x["key"] = []string{"value1", "value2", "value3"}fmt.Println(x)
如果"key"已经存在，你可以使用类型断言（type assertion）来追加元素：
x["key"] = append(x["key"].([]string), "value4", "value5")fmt.Println(x)
输出结果（在Go Playground上尝试示例）：
map[key:[value1 value2 value3]]map[key:[value1 value2 value3 value4 value5]]
注意：你必须重新分配新的切片（由append()返回）。
还要注意，如果"key"尚未存在于映射中或者不是[]string类型，上述代码将会引发错误。为了防止这种错误，只有在值存在且为[]string类型时才进行追加操作：
if s, ok := x["key"].([]string); ok {x["key"] = append(s, "value4", "value5")} else {// 要么缺失，要么不是 []string 类型x["key"] = []string{"value4", "value5"}}
在Go Playground上尝试这个示例。
英文:
You can only append to slices, not to maps.
To add the value you listed, use:
x["key"] = []string{"value1","value2","value3"}fmt.Println(x)
If "key" already exists, you may use type assertion to append to it:
x["key"] = append(x["key"].([]string), "value4", "value5")fmt.Println(x)
Output (try the examples on the Go Playground):
map[key:[value1 value2 value3]]map[key:[value1 value2 value3 value4 value5]]
Note: you have to reassign the new slice (returned by append()).
Also note that if "key" is not yet in the map or is not of type []string, the above code will panic. To protect against such panic, only append if the value exists and is of type []string:
if s, ok := x["key"].([]string); ok {x["key"] = append(s, "value4", "value5")} else {// Either missing or not []stringx["key"] = []string{"value4", "value5"}}
Try this one on the Go Playground.
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