How to Unmarshal JSON Data with Unknown or Variable Keys in Go?

Unmarshal JSON Data of Unknown Format with Variable Keys

When dealing with JSON data that has unknown or variable keys, it can be challenging to define a specific GoLang struct for unmarshalling purposes. This article addresses this problem by providing two viable solutions.

Solution 1: Using map[string]interface{}

If you do not have any knowledge about the keys present in the JSON payload, you can utilize a map with a string key and an interface{} value (i.e., map[string]interface{}). This approach allows for dynamic unmarshalling of the data without requiring a predefined struct. For example:

var grades map[string]interface{}

err := json.Unmarshal([]byte(jsonString), &grades)
fmt.Println(err)
fmt.Printf("%#v\n", grades)

Solution 2: Using a Struct with Ignored Fields

If you still wish to use a struct but want to ignore unknown fields during unmarshalling, you can use the json:"-" tag for those fields. This tag instructs the JSON decoder to not consider these fields during the process. For instance:

type GradeData struct {
    Grades map[string]interface{} `json:"-"`
}

err := json.Unmarshal([]byte(jsonString), &gradesData.Grades)
fmt.Println(err)
fmt.Printf("%#v\n", gradesData)

Both solutions offer flexibility in handling JSON data with unknown or variable keys. However, for further processing or data manipulation, you may need to cast the data to specific types depending on your requirements.

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