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Summary
For quick reference, the following table offers a thorough analysis of the distinctive characteristics, applicability, examples, benefits, and drawbacks of each behavioral design pattern.
| Pattern Name | Distinctive Feature | Applicability | An Example | Pros | Cons |
|---|---|---|---|---|---|
| Iterator | Provides a way to access elements of a collection sequentially without exposing its underlying representation | When you need to provide a standard way to traverse through a collection without exposing its implementation | Browsing through a playlist | Simplifies client code and hides complexity of the collection | Iterator state management can be complex |
| Strategy | Enables an algorithm's behavior to be selected at runtime | When there are multiple ways to achieve a task and you want to determine the algorithm at runtime | Different compression algorithms | Flexibility to switch algorithms; isolation of algorithm implementation | Complexity due to additional classes; clients must be aware of different strategies |
| Template Method | Defines the skeleton of an algorithm in an operation, deferring some steps to subclasses | When the core structure of an algorithm should not change, yet some steps are open to being overridden | Frameworks defining application structure | Promotes code reuse and enforces a predefined algorithm structure | Can lead to less flexibility in subclasses; harder to maintain |
| Observer | Notifies multiple objects about state changes | When changes in one object's state require other objects to be notified | Real-time data feeds | Loose coupling between subject and observers | Risk of unintended performance issues |
| Command | Encapsulates a request as an object | For operations that need to be executed, undone, or logged | User actions in GUI applications | Decouples command execution from usage | Can lead to numerous concrete command classes |
| State | Allows objects to alter their behavior when their internal state changes | For objects whose behavior depends on their state and can change at runtime | Different modes in a game | Localizes state-specific behaviors | Increases the number of classes |
| Chain of Responsibility | Delegates commands to a chain of processing objects | For scenarios where multiple objects can handle a request, but the handler is unknown | Help systems in applications | Decouples request sender and receiver | Handling can become inefficient |
| Mediator | Centralizes complex communications between related objects | To reduce direct communications between multiple objects | Chat application | Simplifies interactions between groups of objects | Mediator can become overly complex |
| Memento | Captures and externalizes an object's internal state | For undo functionality or state save-and-restore | Undo feature in editors | Preserves encapsulation boundaries | Can be memory-intensive |
| Visitor | Separates an algorithm from the objects on which it operates | When operations need to be performed on a group of similar kinds of objects | Processing different types of document elements in a word processor | Simplifies adding new operations; centralizes related operations | Can lead to a bloated visitor interface; harder to maintain when the object structure changes |
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