How to Unmarshal a JSON String Field into a Slice of Strings in Golang?

Custom Unmarshal with String Split in Golang

Problem:

Unmarshalling JSON into a Golang struct, where one string field (e.g., "subjects") needs to be split into a slice of strings based on a delimiter (e.g., '-').

Solution:

Implement a custom unmarshaler for the slice of strings field. This involves creating a new data type that implements the json.Unmarshaler interface:

<code class="go">type strslice []string

func (ss *strslice) UnmarshalJSON(data []byte) error {
    var s string
    if err := json.Unmarshal(data, &s); err != nil {
        return err
    }
    *ss = strings.Split(s, "-")
    return nil
}</code>

Use this custom type in the struct:

<code class="go">type Student struct {
    StudentNumber int      `json:"student_number"`
    Name          string   `json:"name"`
    Subjects      strslice `json:"subjects"`
}</code>

Now, when unmarshalling JSON, the "subjects" field will be automatically split into a slice of strings:

<code class="go">var s Student
err := json.Unmarshal([]byte(src), &s)
fmt.Println(s, err)</code>

Output:

{1234567 John Doe [Chemistry Maths History Geography]} <nil>

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