Free  Understanding Design Patterns - Command

Encapsulates a request as an object, thereby letting you parameterize other objects with different requests, queue or log requests, and support undoable operations. Battles are meant to be won, and no battle can be w...

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Free  Understanding Design Patterns - Observer

Defines a one-to-many dependency between objects so that when on object changes state, all of its dependents are notified and updated automatically. Mary just became a new Mom! Like all new mothers, she is very excit...

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Free  Understanding Design Patterns - Singleton

Ensures a class has only one instance, and provides a global point of access of it. The health clinic has recently offered free medicines if you come in for a checkup. The promotional stint is wo...

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Free  Understanding Design Patterns - Abstract Factory

Provide an interface for creating families of related or dependent objects without specifying their concrete classes. Business is bombing at Dragon Inc. and the CEO wants to franchise all overseas branches. ...

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Free  Understanding Design Patterns - Factory Method

Define an interface for creating an object, but let the classes that implement the interface decide which class to instantiate. The Factory method lets a class defer instantiation to subclasses. ...

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