如何确保首先解析根结构的字段，然后解析嵌入式结构的字段

Question

I have the struct as follows:-

type Inner struct {
    FooInner string `json:"fooInner"`
    BarInner string `json:"barInner,omitempty"`
}

type Root struct {
    Inner
    Foo string `json:"foo"`
    Bar string `json:"bar"`
}

I want the fields of "Root" struct to be parsed first and then the fields of the "Inner" struct. But here the fields of Inner struct is getting parsed first.

Answer 1

If you are asking about JSON marshaling (which is not parsing) and want fields marshaled in a certain order, a marshaler will typically marshal fields in their index order & recurse any embedded structs along the way. Struct field indices - as seen by the reflect package that json.Marhsal uses - are defined by their order of appearance in your code.

So put the fields you want first - and any embedded structs later:

type Root struct {
    Foo string `json:"foo"`
    Bar string `json:"bar"`
    Inner // <- move this last
}

Playground Example

b, _ := json.Marshal(Root{})

{"foo":"","bar":"","fooInner":""}