Golang Mapping Two Keys to a Single Member in JSON Struct
Introduction
In the world of JSON processing, it’s not uncommon to come across scenarios where you need to map multiple keys to a single member in a JSON struct. This can be particularly useful when dealing with data from different sources or when handling legacy systems with inconsistent naming conventions. In this blog post, we will explore how to accomplish this mapping in Golang using the json.Unmarshal functions.
Mapping Two Keys:
Let’s say we have a JSON struct called Response with the following definition:
type Response struct {
Passed bool `json:"passed"`
Results string `json:"results"`
// other fields
}
Now, imagine we receive JSON data from two different sources, where one source uses the key "passed" and the other source mistakenly uses the key "passeds". Our goal is to map both keys to the Passed member of the Response struct, allowing us to handle data from both sources seamlessly.
Implementing UnmarshalJSON
Similarly, we need to implement the UnmarshalJSON method to handle the reverse mapping during JSON decoding. Here’s an example implementation:
func (pr *Response) UnmarshalJSON(data []byte) error {
// Define a struct with fields for both keys
type Alias Response
temp := struct {
Alias
Passeds bool `json:"passeds"`
}{}
// Unmarshal JSON into the temporary struct
if err := json.Unmarshal(data, &temp); err != nil {
return err
}
// Assign the values from the temporary struct to the actual struct
pr.Passed = temp.Passeds || temp.Passed
pr.Results = temp.Results
return nil
}
Check out complete code at https://goplay.tools/snippet/a6_GcLfQigN
In this implementation, we create an auxiliary struct that includes the Passed member alongside the alias. We unmarshal the JSON data into this auxiliary struct and then assign the value of Passeds to the Passed member of the Response struct.
Conclusion
By implementing the UnmarshalJSON methods for the Response struct, we can seamlessly handle JSON data with different key names. This allows us to map two keys to a single member in the JSON struct and achieve greater flexibility and compatibility in our applications.
Mapping keys in JSON structs is just one example of how Golang’s flexibility and powerful JSON processing capabilities can help us handle complex data scenarios. With a deeper understanding of JSON encoding and decoding, we can build robust and adaptable applications that gracefully handle diverse data sources.
I hope this blog post has provided valuable insights into mapping two keys to a single member in JSON structs using Golang. Feel free to explore further and experiment with different scenarios to enhance your JSON processing capabilities.