1. Creational Patterns

Welcome to the Design Patterns wiki!

1. Creational Patterns:

1. Abstract Factory

Provide an interface for creating families of related or dependent objects without specifying their concrete classes.

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Use the Abstract Factory pattern when…

• A system should be independent of how its products are created, composed, and represented.
• A system can be configured with one of multiple families of products.
• The constraint requiring products from the same factory to be used together must be enforced.
• The emphasis is on revealing interfaces, not implementations.

2. Builder

Separate the construction of a complex object from its representation so that the same construction process can create different representations.

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Use the Builder pattern when…

• The algorithm for creating parts is independent from the parts themselves.
• The object to be assembled might have different representations.
• You need fine control over the construction process.

3. Factory Method

Define an interface for creating an object, but let subclasses decide which class to instantiate. Factory Method lets a class defer instantiation to subclasses.

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Use the Factory Method pattern when…

• Flexibility is important.
• Objects can be extended in subclasses
• There is a specific reason why one subclass would be chosen over another—this logic forms part of the Factory Method.
• A client delegates responsibilities to subclasses in parallel hierarchies. Consider using instead....
• The Abstract Factory, Prototype, or Builder patterns, which are more flexible (though also more complex).
• The Prototype pattern to store a set of objects to clone from the abstract factory.

4. Prototype

Specify the kind of objects to create using a prototypical instance, and create new objects by copying this prototype.

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Use the Prototype pattern when… You want to:

• Hide concrete classes from the client.
• Add and remove new classes (via prototypes) at runtime.
• Keep the number of classes in the system to a minimum.
• Adapt to changing structures of data at runtime.

5. Singleton

Ensure a class has only one instance and provide a global point of access to it.

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Use the Singleton pattern when …

• You need to ensure there is only one instance of a class.
• Controlled access to that instance is essential.
• You might need more than one instance at a later stage.
• The control should be localized in the instantiated class, not in some other mechanism.

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