Design Pattern

Concise, visual, and practical explanations of software design patterns for architecture, prototyping, and implementation.

The goal is to explain recurring design solutions in a way that is easy to understand, architecturally useful, and directly relevant for software development and prototyping. Each pattern should be described with a clear intent, a minimal diagram, and a short explanation of its internal logic. The focus is on correct, trustfull design pattern supporting a clear understanding of the parttern goals, structure, and practical relevance.

A design pattern is a proven, reusable solution to a recurring design problem in software. It does not prescribe one fixed implementation. Instead, it provides a structured way to think about responsibilities, interactions, and trade-offs in a system.

Facade Pattern

The Facade Pattern provides a simple and stable entry point to a more complex internal subsystem. It reduces the amount of internal knowledge a client needs in order to use a set of related components. This makes external usage easier, while internal structure and orchestration can remain hidden behind the facade.

flowchart LR
    C[Client] --> F[Facade]
    F --> A[Subsystem A]
    F --> B[Subsystem B]
    F --> C2[Subsystem C]

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• The client interacts with one clear entry point instead of multiple internal components.
• The facade delegates requests to the relevant subsystems behind the scenes.
• This reduces outward complexity and stabilizes the external interface.
• The internal structure may change without forcing every client to change with it.

sequenceDiagram
    participant C as Client
    participant F as Facade
    participant A as Subsystem A
    participant B as Subsystem B
    participant D as Subsystem C

    C->>F: Request
    F->>A: Partial call 1
    A-->>F: Result 1
    F->>B: Partial call 2
    B-->>F: Result 2
    F->>D: Partial call 3
    D-->>F: Result 3
    F-->>C: Consolidated response

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This sequence diagram shows how the Facade Pattern handles a client request through one central entry point.

• The client sends a single request to the facade, which then coordinates several internal subsystem calls in the required order.
• Each subsystem returns its partial result to the facade instead of responding directly to the client.
• The facade combines these internal results and returns one consolidated response, hiding the underlying complexity from the client.

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