"State" is a design pattern in software development that belongs to the category of behavioral patterns. It allows an object to change its behavior when its internal state changes, making it appear as if it has switched its class.
The State pattern is used to implement situation-dependent behavior, where the behavior of an object depends on its internal state. It helps to avoid large and complex state machines by externalizing the state and the corresponding behavioral logic into separate classes.
The fundamental components of the State pattern are:
Context: This is the context object that represents the current state. It holds a reference to the current state object and delegates requests to the state object to perform actions. The context can also provide methods to change the state.
State: This is the abstract interface that defines the methods describing the behavior for different states. Each concrete state class implements this interface and handles the requests according to its state.
ConcreteState: These are the concrete implementations of the State interface, defining the behavior for specific states. Each state takes control of the behavior when the context object is in that state.
The State pattern allows an object to change its behavior by transitioning between different states. When the object switches to a new state, it effectively switches to a different implementation of behavior without the client class or the context object needing to know or be affected.
The State pattern is often used in situations where an object's behavior changes depending on the context or state, such as in state machines, user interface controls, or other use cases where an object's state influences its possible behavior. It promotes clean and flexible code organization, as states can be easily added or changed without requiring significant modifications to the affected classes.
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