Golang: Getting only one object in a JSON collection response-CodePudding

Suppose I have have a JSON response body that looks something like this:

{
   value: [{Object A's key-values}, {Object B's key-values}, {Object C's key-values} ...]
}

Where Object A, B, C are of different structures, although they may have same key names. (e.g. both Obj A and B could have the key "b", but only Obj A has the key "a")

I am only interested in Object A from the JSON response, the rest can be discarded. If I have a structure like this:

type MyObject struct{
    a string
    b string
}

type MyData struct{
   value []MyObject
}

Will unmarshalling the response into MyData work? Can we specify a slice of a particular type such that only the desired element with the correct structure gets unmarhshalled and the rest of the objects in the JSON collection gets ignored?

CodePudding user response：

First: you need to export struct members:

type MyObject struct{
    A string `json:"a"`
    B string `json:"b"`
}
type MyData struct{
   Value []MyObject `json:"value"`
}

Then, you can unmarshal the array using:

var v MyData
json.Unmarshal(input,&v)

This will create a MyObject instance for every array element in the input, but only those that have a and b fields will be populated. Thus, you can filter the ones containing a:

for _,x:=range v.Values {
   if x.A!="" {
     ///
   }
}