橋接模式
橋接模式是軟件設計模式中最複雜的模式之一，它把事物對象和其具體行爲、具體特徵分離開來，使它们可以各自独立的变化。事物對象僅是一個抽象的概念。如“圓形”、“三角形”歸于抽象的“形狀”之下，而“畫圓”、“畫三角”歸于實現行爲的“畫圖”類之下，然後由“形狀”調用“畫圖”。
結構
- Abstraction
- 定義抽象的介面
- 該介面包含實現具體行爲、具體特徵的Implementor介面
- Refined Abstraction
- 抽象介面Abstraction的子類，依舊是一個抽象的事物名
- Implementor
- 定義具體行爲、具體特徵的應用介面
- ConcreteImplementor
- 實現Implementor介面
示例
下列各語言的代碼都用於寫出兩個不同的圓的坐標和半徑。
API1.circle at 1:2 7.5 API2.circle at 5:7 27.5
Java
/** "Implementor" */
interface DrawingAPI
{
public void drawCircle(double x, double y, double radius);
}
/** "ConcreteImplementor" 1/2 */
class DrawingAPI1 implements DrawingAPI
{
public void drawCircle(double x, double y, double radius)
{
System.out.printf("API1.circle at %f:%f radius %f\n", x, y, radius);
}
}
/** "ConcreteImplementor" 2/2 */
class DrawingAPI2 implements DrawingAPI
{
public void drawCircle(double x, double y, double radius)
{
System.out.printf("API2.circle at %f:%f radius %f\n", x, y, radius);
}
}
/** "Abstraction" */
interface Shape
{
public void draw(); // low-level
public void resizeByPercentage(double pct); // high-level
}
/** "Refined Abstraction" */
class CircleShape implements Shape
{
private double x, y, radius;
private DrawingAPI drawingAPI;
public CircleShape(double x, double y, double radius, DrawingAPI drawingAPI)
{
this.x = x; this.y = y; this.radius = radius;
this.drawingAPI = drawingAPI;
}
// low-level i.e. Implementation specific
public void draw()
{
drawingAPI.drawCircle(x, y, radius);
}
// high-level i.e. Abstraction specific
public void resizeByPercentage(double pct)
{
radius *= pct;
}
}
/** "Client" */
class BridgePattern {
public static void main(String[] args)
{
Shape[] shapes = new Shape[2];
shapes[0] = new CircleShape(1, 2, 3, new DrawingAPI1());
shapes[1] = new CircleShape(5, 7, 11, new DrawingAPI2());
for (Shape shape : shapes)
{
shape.resizeByPercentage(2.5);
shape.draw();
}
}
}
C#
using System;
/** "Implementor" */
interface IDrawingAPI {
void DrawCircle(double x, double y, double radius);
}
/** "ConcreteImplementor" 1/2 */
class DrawingAPI1 : IDrawingAPI {
public void DrawCircle(double x, double y, double radius)
{
System.Console.WriteLine("API1.circle at {0}:{1} radius {2}", x, y, radius);
}
}
/** "ConcreteImplementor" 2/2 */
class DrawingAPI2 : IDrawingAPI
{
public void DrawCircle(double x, double y, double radius)
{
System.Console.WriteLine("API2.circle at {0}:{1} radius {2}", x, y, radius);
}
}
/** "Abstraction" */
interface IShape {
void Draw(); // low-level (i.e. Implementation-specific)
void ResizeByPercentage(double pct); // high-level (i.e. Abstraction-specific)
}
/** "Refined Abstraction" */
class CircleShape : IShape {
private double x, y, radius;
private IDrawingAPI drawingAPI;
public CircleShape(double x, double y, double radius, IDrawingAPI drawingAPI)
{
this.x = x; this.y = y; this.radius = radius;
this.drawingAPI = drawingAPI;
}
// low-level (i.e. Implementation-specific)
public void Draw() { drawingAPI.DrawCircle(x, y, radius); }
// high-level (i.e. Abstraction-specific)
public void ResizeByPercentage(double pct) { radius *= pct; }
}
/** "Client" */
class BridgePattern {
public static void Main(string[] args) {
IShape[] shapes = new IShape[2];
shapes[0] = new CircleShape(1, 2, 3, new DrawingAPI1());
shapes[1] = new CircleShape(5, 7, 11, new DrawingAPI2());
foreach (IShape shape in shapes) {
shape.ResizeByPercentage(2.5);
shape.Draw();
}
}
}
用generics類庫的C#
using System;
/** "Implementor" */
interface IDrawingAPI {
void DrawCircle(double x, double y, double radius);
}
/** "ConcreteImplementor" 1/2 */
struct DrawingAPI1 : IDrawingAPI {
public void DrawCircle(double x, double y, double radius)
{
System.Console.WriteLine("API1.circle at {0}:{1} radius {2}", x, y, radius);
}
}
/** "ConcreteImplementor" 2/2 */
struct DrawingAPI2 : IDrawingAPI
{
public void DrawCircle(double x, double y, double radius)
{
System.Console.WriteLine("API2.circle at {0}:{1} radius {2}", x, y, radius);
}
}
/** "Abstraction" */
interface IShape {
void Draw(); // low-level (i.e. Implementation-specific)
void ResizeByPercentage(double pct); // high-level (i.e. Abstraction-specific)
}
/** "Refined Abstraction" */
class CircleShape<T> : IShape
where T : struct, IDrawingAPI
{
private double x, y, radius;
private static IDrawingAPI drawingAPI = new T();
public CircleShape(double x, double y, double radius)
{
this.x = x; this.y = y; this.radius = radius;
}
// low-level (i.e. Implementation-specific)
public void Draw() { drawingAPI.DrawCircle(x, y, radius); }
// high-level (i.e. Abstraction-specific)
public void ResizeByPercentage(double pct) { radius *= pct; }
}
/** "Client" */
class BridgePattern {
public static void Main(string[] args) {
IShape[] shapes = new IShape[2];
shapes[0] = new CircleShape<DrawingAPI1>(1, 2, 3);
shapes[1] = new CircleShape<DrawingAPI2>(5, 7, 11);
foreach (IShape shape in shapes) {
shape.ResizeByPercentage(2.5);
shape.Draw();
}
}
}
C++
#include <iostream>
using namespace std;
/* Implementor*/
class DrawingAPI {
public:
virtual void drawCircle(double x, double y, double radius) = 0;
virtual ~DrawingAPI() {}
};
/* Concrete ImplementorA*/
class DrawingAPI1 : public DrawingAPI {
public:
void drawCircle(double x, double y, double radius) {
cout << "API1.circle at " << x << ':' << y << ' ' << radius << endl;
}
};
/* Concrete ImplementorB*/
class DrawingAPI2 : public DrawingAPI {
public:
void drawCircle(double x, double y, double radius) {
cout << "API2.circle at " << x << ':' << y << ' ' << radius << endl;
}
};
/* Abstraction*/
class Shape {
public:
virtual ~Shape() {}
virtual void draw() = 0;
virtual void resizeByPercentage(double pct) = 0;
};
/* Refined Abstraction*/
class CircleShape : public Shape {
public:
CircleShape(double x, double y,double radius, DrawingAPI *drawingAPI) :
m_x(x), m_y(y), m_radius(radius), m_drawingAPI(drawingAPI)
{}
void draw() {
m_drawingAPI->drawCircle(m_x, m_y, m_radius);
}
void resizeByPercentage(double pct) {
m_radius *= pct;
}
private:
double m_x, m_y, m_radius;
DrawingAPI *m_drawingAPI;
};
int main(void) {
DrawingAPI1 dap1;
DrawingAPI2 dap2;
CircleShape circle1(1,2,3,&dap1);
CircleShape circle2(5,7,11,&dap2);
circle1.resizeByPercentage(2.5);
circle2.resizeByPercentage(2.5);
circle1.draw();
circle2.draw();
return 0;
}
Python
# Implementor
class DrawingAPI:
def drawCircle(x, y, radius):
pass
# ConcreteImplementor 1/2
class DrawingAPI1(DrawingAPI):
def drawCircle(self, x, y, radius):
print "API1.circle at %f:%f radius %f" % (x, y, radius)
# ConcreteImplementor 2/2
class DrawingAPI2(DrawingAPI):
def drawCircle(self, x, y, radius):
print "API2.circle at %f:%f radius %f" % (x, y, radius)
# Abstraction
class Shape:
# low-level
def draw(self):
pass
# high-level
def resizeByPercentage(self, pct):
pass
# Refined Abstraction
class CircleShape(Shape):
def __init__(self, x, y, radius, drawingAPI):
self.__x = x
self.__y = y
self.__radius = radius
self.__drawingAPI = drawingAPI
# low-level i.e. Implementation specific
def draw(self):
self.__drawingAPI.drawCircle(self.__x, self.__y, self.__radius)
# high-level i.e. Abstraction specific
def resizeByPercentage(self, pct):
self.__radius *= pct
def main():
shapes = [
CircleShape(1, 2, 3, DrawingAPI1()),
CircleShape(5, 7, 11, DrawingAPI2())
]
for shape in shapes:
shape.resizeByPercentage(2.5)
shape.draw()
if __name__ == "__main__":
main()
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