Structural Design Patterns

Structural Design Patterns - Adapter

Structural Design Patterns in Swift

Adapter: To unify the interfaces of incompatible classes that already exists

Bridge: It decouples abstraction from its implementation, so that we can change them independently. It reduces the impact of changes

Decorator: Used to add new responsibilities to objects without modifying the underlying classes

Composite pattern: Describes how to combine objects so that each of them can be either simple or composite object.

Facade: Allows us to expose functionality of entire sub system via single class

Fly weight pattern: Used to effectively sharing no. of instances of a class by reducing number of object instances at runtime.

Proxy pattern: Proxy objects acts as a surrogate for more complex objects that me expensive for create or use.

Adapter: This pattern maps the existing interface to other interface.

Eg., Two classes A and B are implementing a protocol P, so we use polymorphism to call the methods of A and B classes. Now when a new class C does not implement the protocol P and we need to use the class C along with A and B, we couldn’t do it as the interface is different. In order to add the new method/interface to C (similar to A and B) we need Adapter Pattern

Adapter Pattern can be used in two ways

Creating new adapter class:
Creating class D which adopts method protocol P and insod

protocol P {
func shareMessage(msg: String)
}
class D: P {
func shareMessage(msg: String) {
someObjectWithDifferentInterface.differentMethod(message: msg)
}
}
Extending existing class to add new functionality:

extension C: P {
func shareMessage(msg: String) {
someObjectWithDifferentInterface.differentMethod(message: msg)
}
}