What does the required keyword in Swift mean?

The required keyword in Swift is used to ensure that a specific initializer must be implemented by all subclasses of the class where the keyword is used. This means that any subclass must provide its own implementation of the initializer marked as required, or inherit it if it can satisfy the requirement with an inherited initializer.

Key Points about required Keyword:

1. Mandatory Implementation:

   • When an initializer is marked with the required keyword, any subclass of the class must implement this initializer. This ensures that the initializer is available in all subclasses, maintaining a consistent initialization interface across the class hierarchy[1][6].

2. No override Needed:

   • When implementing a required initializer in a subclass, the override keyword is not needed. The required keyword implies that the initializer is being overridden, and the compiler will enforce this requirement[1][6].

3. Usage in Protocols:

   • The required keyword is also used when implementing initializers that are required by a protocol. This ensures that any class conforming to the protocol will implement the necessary initializers[1].

4. Final Classes:

   • If a class is marked as final, it cannot be subclassed, and therefore, the required keyword is not needed. The final keyword effectively makes the use of required redundant in such cases[1][3].

5. Example:

   swift Copy

   class Vehicle {
       var vehicleType: String
   
       required ...