Bridge Pattern
The intent is to separate the abstraction from the implementation so that both can evolve independently.
UML
https://www.runoob.com/design-pattern/bridge-pattern.html
Used in Qt:
abstraction
class QPaintDevice{
public:
virtual QPaintEngine * paintEngine() const = 0;
``````
}implementation
class QPaintEngine{
public:
``````
}
Client Code:
class QPainter{
public:
```````
}
Some Codes:
1. Define the Implementor (Interface for implementation)
#include <iostream>
#include <memory>// Implementor interface
class DrawingAPI {
public:virtual ~DrawingAPI() = default;virtual void drawCircle(double x, double y, double radius) = 0;
};// Concrete Implementor 1
class DrawingAPI1 : public DrawingAPI {
public:void drawCircle(double x, double y, double radius) override {std::cout << "Drawing Circle with API1 at (" << x << ", " << y << ") with radius " << radius << std::endl;}
};
2. Create Concrete Implementors
// Concrete Implementor 2
class DrawingAPI2 : public DrawingAPI {
public:void drawCircle(double x, double y, double radius) override {std::cout << "Drawing Circle with API2 at (" << x << ", " << y << ") with radius " << radius << std::endl;}
};
3. Define the Abstraction
// Abstraction
class Shape {
public:virtual ~Shape() = default;virtual void draw() = 0;virtual void resize(double factor) = 0;
};
4. Refine the Abstraction (Extend the Abstraction)
// Refined Abstraction
class CircleShape : public Shape {
private:std::shared_ptr<DrawingAPI> drawingAPI;double x, y, radius;public:CircleShape(std::shared_ptr<DrawingAPI> api, double x, double y, double radius): drawingAPI(std::move(api)), x(x), y(y), radius(radius) {}void draw() override {drawingAPI->drawCircle(x, y, radius); // Delegate the drawing task to the DrawingAPI}void resize(double factor) override {radius *= factor; // Resize the circle by a factor}
};5. Client Code
int main() {// Create a circle using DrawingAPI1std::shared_ptr<DrawingAPI> api1 = std::make_shared<DrawingAPI1>();std::shared_ptr<Shape> circle1 = std::make_shared<CircleShape>(api1, 1.0, 2.0, 3.0);// Create a circle using DrawingAPI2std::shared_ptr<DrawingAPI> api2 = std::make_shared<DrawingAPI2>();std::shared_ptr<Shape> circle2 = std::make_shared<CircleShape>(api2, 4.0, 5.0, 6.0);// Draw the circlescircle1->draw();circle2->draw();// Resize the circlescircle1->resize(2.0);circle2->resize(0.5);// Draw the circles again after resizingcircle1->draw();circle2->draw();return 0;
}
