How to Define the Operator ‘[]’ for the Type ‘Object’ in Dart

With Dart, you may encounter an error message that says “the operator ‘[]’ isn’t defined for the type ‘object’. try defining the operator ‘[]’.” This error occurs when you’re trying to use the indexing operator on an object that doesn’t have the ‘[]’ operator defined. In this tutorial, we’ll show you how to define the ‘[]’ operator for the ‘Object’ type in Dart.

Define the ‘[]’ Operator: To define the ‘[]’ operator for the ‘Object’ type, you need to create a class that implements the ‘Map’ interface. The ‘Map’ interface defines the ‘[]’ operator and other methods that allow you to access and modify the contents of the map.

class MyObject {
  Map<String, dynamic> _data = {};

  operator [](String key) => _data[key];
  operator []=(String key, value) => _data[key] = value;
}

In this example, we created a class called ‘MyObject’ that contains a private ‘_data’ map. We defined the ‘[]’ operator and the ‘[]=’ operator to access and modify the values in the ‘_data’ map.

Use the ‘[]’ Operator: Once you’ve defined the ‘[]’ operator for your object, you can use it to access the values stored in your object.

MyObject myObject = MyObject();
myObject['name'] = 'John';
myObject['age'] = 30;

print(myObject['name']); // Output: John
print(myObject['age']); // Output: 30

That’s it! By defining the ‘[]’ operator for the ‘Object’ type, you can now use the indexing operator on your objects and avoid the error message.