How Can I Effectively Parse Complex JSON Structures Using Go's `json.Unmarshal`?

Parsing Complex JSON with Go Unmarshal

In Go, the encoding/json package provides the json.Unmarshal function to parse JSON data. This data can be unmarshaled into a predefined struct or an interface{} type for iterating unexpected data structures. However, parsing complex JSON can be challenging.

For instance, consider the following JSON:

{
  "k1": "v1",
  "k2": "v2",
  "k3": 10,
  "result": [
    [
      ["v4", "v5", {"k11": "v11", "k22": "v22"}],
      ...
      ["v4", "v5", {"k33": "v33", "k44": "v44"}]
    ],
    "v3"
  ]
}

To parse this JSON using json.Unmarshal, we can create an interface{} variable and store the parsed result in it:

type MyData struct {
  v1 string
  v2 string
  v3 int
  result [][]MySubData
  result2 string
}

type MySubData struct {
  v1 string
  v2 string
  result map[string]string
}

var f interface{}
err := json.Unmarshal(b, &f)

After unmarshaling, the f variable will be a map with string keys and empty interface values. To access this data, we use a type assertion to convert f into a map[string]interface{} and iterate through it:

m := f.(map[string]interface{})
for k, v := range m {
  switch vv := v.(type) {
    case string:
      // Handle string values
    case int:
      // Handle integer values
    case []interface{}:
      // Handle array values
    default:
      // Handle unknown types
  }
}

This approach allows us to work with unexpected JSON data structures while maintaining type safety. For more details, refer to the original article on JSON and Go.

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