How to Decode JSON with an Unknown Structure in Go?

Decoding JSON with Unknown Structure

In the realm of programming, JSON (JavaScript Object Notation) often serves as a means of representing data within software applications. However, when encountering JSON with an unfamiliar structure, extracting specific information can pose a challenge. Consider the following scenario:

You need to process a JSON string like this:

{ 
  "votes": { 
    "option_A": "3" 
  } 
}

Your goal is to augment this JSON by including a "count" key, resulting in the following output:

{ 
  "votes": { 
    "option_A": "3" 
  }, 
  "count": "1" 
}

The challenge arises from the unknown structure of the initial JSON. Traditional methods, such as using the json.Unmarshal function with a specific typed struct, become inapplicable.

Solution: Unmarshal into a Map

To overcome this obstacle, we can leverage the flexibility of Go's maps. The following code snippet demonstrates how to unmarshal JSON into a map[string]interface{}:

package main

import (
    "encoding/json"
    "fmt"
)

func main() {
    in := []byte(`{ 
      "votes": { 
        "option_A": "3" 
      } 
    }`)
    var raw map[string]interface{}
    if err := json.Unmarshal(in, &raw); err != nil {
        panic(err)
    }
    
    // Modify the map by adding the "count" key
    raw["count"] = 1
    
    // Marshal the modified map back to JSON
    out, err := json.Marshal(raw)
    if err != nil {
        panic(err)
    }
    
    fmt.Println(string(out))
}

By unmarshaling the JSON into a map, we effectively create a type-agnostic data structure that can accommodate any input. It allows us to dynamically access and modify the JSON content without relying on predefined types.

The final output of the above code is as follows:

{ 
  "votes": { 
    "option_A": "3" 
  }, 
  "count": "1" 
}

This approach provides a convenient and flexible solution for decoding JSON with unknown structures, empowering developers to extract and manipulate data efficiently.

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