英文:
getting nullable object on json unmarshal in golang
问题
以下是翻译好的内容：
package mainimport ("encoding/json""fmt""io/ioutil""os")type student struct {ID string `json:"id"`Name string `json:"name"`Standard string `json:"std"`}type cls struct {st student `json:"cls"`}func getValues() (cls, error) {var clss clsdataBytes, err := ioutil.ReadFile("studentclass.json")if err != nil {fmt.Printf("文件错误：%v\n", err)os.Exit(1)}err = json.Unmarshal(dataBytes, &clss)if err != nil {fmt.Errorf("%s", err)}return clss, err}func main() {s, err := getValues()fmt.Printf("%#v\n", s)fmt.Println(err)}
{"cls": {"id": "1","name": "test","std": "0"}}
当我运行 go run jsonTestParse.go 时，它给出了以下输出：
main.cls{st:main.student{ID:"", Name:"", Standard:""}}<nil>
请帮我解释为什么我得到了这个空对象：
main.cls{st:main.student{ID:"", Name:"", Standard:""}}
而不是这个：
main.cls{st:main.student{ID:"1", Name:"test", Standard:"0"}}
另外，如何获取这些值会很有帮助？
英文:
> Go code(jsonTestParse.go)
>
> (this is just a test example I made, please don't argue that I should
> use list of students in cls struct)
package mainimport ("encoding/json""fmt""io/ioutil""os")type student struct {ID string `json:"id"`Name string `json:"name"`Standard string `json:"std"`}type cls struct {st student `json:"cls"`}func getValues() (cls, error) {var clss clsdataBytes, err := ioutil.ReadFile("studentclass.json")if err != nil {fmt.Printf("File error: %v\n", err)os.Exit(1)}err = json.Unmarshal(dataBytes, &clss)if err != nil {fmt.Errorf("%s", err)}return clss, err}func main() {s, err := getValues()fmt.Printf("%#v\n", s)fmt.Println(err)}
> Json File (studentclass.json)
{"cls": {"id": "1","name": "test","std": "0"}}
When I run this code with go run jsonTestParse.go it gives me this output:
main.cls{st:main.student{ID:"", Name:"", Standard:""}}<nil>
Please help me why I'm getting this blank object
main.cls{st:main.student{ID:"", Name:"", Standard:""}}
instead of this
main.cls{st:main.student{ID:"1", Name:"test", Standard:"0"}}
Plus It would be great to help on how to get these values?
答案1
得分: 3
这是因为你的 cls 结构体中嵌入了私有结构体（小写未导出字段） student st，将其改为导出字段应该可以解决问题，即：
type cls struct {// St 字段将被反序列化St student `json:"cls"`}
在 playground 中查看。
英文:
That is because your cls struct has embedded private struct (lower case unexported field) of student st, change to exported field should work, that is:
type cls struct {// St field will be unmarshalledSt student `json:"cls"`}
See in playground
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