JsonDecoder class Null safety

This class parses JSON strings and builds the corresponding objects.

A JSON input must be the JSON encoding of a single JSON value, which can be a list or map containing other values.

Throws FormatException if the input is not valid JSON text.

Example:

const JsonDecoder decoder = JsonDecoder();

const String jsonString = '''
  {
    "data": [{"text": "foo", "value": 1 },
             {"text": "bar", "value": 2 }],
    "text": "Dart"
  }
''';

final Map<String, dynamic> object = decoder.convert(jsonString);

final item = object['data'][0];
print(item['text']); // foo
print(item['value']); // 1

print(object['text']); // Dart

When used as a StreamTransformer, the input stream may emit multiple strings. The concatenation of all of these strings must be a valid JSON encoding of a single JSON value.