英文:
Having trouble accessing a key in a map inside an []interface
问题
示例代码：
package mainimport "fmt"func main() {example_container := []interface{}{map[string]string{"name": "bob","id": "1",},map[string]string{"name": "jim","id": "2",},}fmt.Printf("%v\n", example_container)fmt.Printf("%v\n", example_container[0])fmt.Printf("%v\n", example_container[0]["name"])}
有问题的行：
fmt.Printf("%v\n", example_container[0]["name"])
错误：
invalid operation: example_container[0]["name"] (type interface {} does not support indexing)
问题：
我如何访问接口内部的键？
我需要定义一个更复杂的接口并设置方法来实现这个吗？
英文:
Example code:
package mainimport "fmt"func main() {example_container := []interface{}{map[string]string{"name": "bob","id": "1",},map[string]string{"name": "jim","id": "2",},}fmt.Printf("%v\n", example_container)fmt.Printf("%v\n", example_container[0])fmt.Printf("%v\n", example_container[0]["name"])}
Problematic line:
fmt.Printf("%v\n", example_container[0]["name"])
Error:
invalid operation: example_container[0]["name"] (type interface {} does not support indexing)
Question:
How do I access the keys inside this interface, then?
Do I have to define a more elaborate interface with a method set to accomplish this?
答案1
得分: 5
由于您的切片类型是[]interface{}，对该切片进行索引将得到interface{}类型的元素。interface{}类型的值无法进行索引。
但是，由于您将map[string]string类型的值放入其中，您可以使用type assertion来获取该映射类型的值，然后可以正确地进行索引：
fmt.Printf("%v\n", example_container[0].(map[string]string)["name"])
输出结果（在Go Playground上尝试）：
[map[name:bob id:1] map[name:jim id:2]]map[name:bob id:1]bob
如果您知道您将始终在example_container切片中存储map[string]string类型的值，最好将其定义如下：
example_container := []map[string]string{map[string]string{"name": "bob","id": "1",},map[string]string{"name": "jim","id": "2",},}
然后，您无需进行类型断言即可访问名称：
fmt.Printf("%v\n", example_container[0]["name"])
在Go Playground上尝试这个示例。
还请注意，在用于初始化example_container切片的复合字面量中，当列出元素时，甚至可以省略映射类型：
example_container := []map[string]string{{"name": "bob","id": "1",},{"name": "jim","id": "2",},}
英文:
Since your slice type is []interface{}, indexing this slice will give you elements of type interface{}. Values of type interface{} cannot be indexed.
But since you put values of type map[string]string into it, you may use type assertion to obtain a value of that map type, which you can index properly:
fmt.Printf("%v\n", example_container[0].(map[string]string)["name"])
Output (try it on the Go Playground):
[map[name:bob id:1] map[name:jim id:2]]map[name:bob id:1]bob
If you know you will always store values of type map[string]string in your example_container slice, best would be to define it like this:
example_container := []map[string]string{map[string]string{"name": "bob","id": "1",},map[string]string{"name": "jim","id": "2",},}
And then you don't need type assertion to access the name:
fmt.Printf("%v\n", example_container[0]["name"])
Try this one on the Go Playground.
Also note that in the composite literal you use to initialize your example_container slice, you can even omit the map type when listing the elements:
example_container := []map[string]string{{"name": "bob","id": "1",},{"name": "jim","id": "2",},}
通过集体智慧和协作来改善编程学习和解决问题的方式。致力于成为全球开发者共同参与的知识库，让每个人都能够通过互相帮助和分享经验来进步。
评论