In what cases and for what purposes is the extension mechanism used in dispatching?

Extension mechanisms in dispatching (for example, in iOS or other systems with dynamic dispatch) are used to add additional behavior or handle calls without modifying the source code of the base class or object. This allows extending the functionality of classes, adding new methods, or changing message handling logic.

The main goals of using extensions in dispatching:

• Adding methods to existing classes without inheritance.
• Organizing code into functional blocks for better readability.
• Implementing protocols and interfaces in separate extensions.
• Dynamically changing object behavior at runtime.

For example, in Swift, extensions allow adding methods to standard types or your own classes without creating subclasses:

extension String {
    func reversedString() -> String {
        return String(self.reversed())
    }
}

let text = "hello"
print(text.reversedString()) // olleh

In message dispatching, extensions help flexibly manage method calls and their processing.