The façade is generally referred to as the face of the building, especially an attractive one. It can be also referred to as a behavior or appearance that gives a false idea of someone's true feelings or situation. When people walk past a façade, they can appreciate the exterior face but aren't aware of the complexities of the structure within. This is how a façade pattern is used. Façade hides the complexities of the internal system and provides an interface to the client that can access the system in a very simplified way.
Consider the example of a storekeeper. Now, when you, as a customer, visit a store to buy certain items, you're not aware of the layout of the store. You typically approach the storekeeper, who is well aware of the store system. Based on your requirements, the storekeeper picks up items and hands them over to you. Isn't this easy? The customer need not know how the store looks and s/he gets the stuff done through a simple interface, the storekeeper.
The Façade design pattern essentially does the following:
- It provides a unified interface to a set of interfaces in a subsystem and defines a high-level interface that helps the client use the subsystem in an easy way.
- Façade discusses representing a complex subsystem with a single interface object. It doesn't encapsulate the subsystem but actually combines the underlying subsystems.
- It promotes the decoupling of the implementation with multiple clients.