C++设计模式——Bridge模式（下）

在上篇《C++设计模式——Bridge模式（上）》中我们对于桥接模式做了一些介绍。介于桥接模式在实际项目开发中使用广泛，而且也是面试中常问常新的话题。在本篇，我们专注bridge模式在具体的项目开发中的应用，举几个例子来说明。

#ifndef SHAPE_H
#define SHAPE_H#include <QObject>
#include <QWidget>
#include <QColor>
#include <QPointF>
#include <QPaintEvent>
#include <QPainter>
#include <QPen>
#include <QBrush>
#include <QDebug>class ShapeImp;class Shape
{public:virtual void draw() = 0;virtual void setLineColor(const QColor& color) = 0;virtual void setLineWidth(const int width) = 0;virtual ~Shape() {}
protected:Shape(ShapeImp* imp) : imp_(imp) {}ShapeImp* imp_;
};class ShapeImp : public QWidget
{
public:virtual void draw() = 0;virtual void setLineColor(const QColor& color) = 0;virtual void setLineWidth(const int width) = 0;virtual ~ShapeImp() {}
protected:ShapeImp(QWidget* parent = nullptr):QWidget(parent) {}friend class Shape;
};class ShapeImpWin : public Shape
{
public:ShapeImpWin(ShapeImp* pImpl) : Shape(pImpl) {}
public: // operationvoid draw() override{ imp_->draw(); }void setLineColor (const QColor& color) override { imp_->setLineColor(color); }void setLineWidth(const int width) override { imp_->setLineWidth(width);}
};class Circle : public ShapeImp
{Q_OBJECT
public:Circle(const QPointF& center,qreal raduis,QWidget* parent = nullptr): m_center(center),m_raduis(raduis),ShapeImp(parent){}void draw(){ update(); }void setLineColor(const QColor& color) override {m_color = color;}void setLineWidth(const int width) override{ m_lineWidth = width; }virtual void paintEvent(QPaintEvent* e) override{QPainter painter(this);QPen pen;pen.setColor( m_color /*QColor(Qt::red)*/);pen.setWidth(m_lineWidth);QBrush brush;brush.setColor(QColor(Qt::lightGray));painter.setPen(pen);painter.setBrush(brush);// draw circlepainter.drawEllipse(m_center,m_raduis,m_raduis);e->accept();}private:QPointF m_center;qreal m_raduis = 50;QColor m_color = QColor(Qt::black);int m_lineWidth = 1;
};class Rectange : public ShapeImp
{Q_OBJECT
public:Rectange(const QPointF& topleft,qreal width,qreal height,QWidget* parent = nullptr): m_topleft(topleft),m_width(width),m_height(height),ShapeImp(parent){}void draw(){ update(); }void setLineColor(const QColor& color) override {m_color = color;}void setLineWidth(const int width) override{ m_lineWidth = width; }virtual void paintEvent(QPaintEvent* e) override{QPainter painter(this);QPen pen;pen.setColor( m_color /*QColor(Qt::red)*/);pen.setWidth(m_lineWidth);QBrush brush;brush.setColor(QColor(Qt::lightGray));painter.setPen(pen);painter.setBrush(brush);// draw circleQRectF r(m_topleft.x(),m_topleft.y(),m_width,m_height);painter.drawRect(r);qDebug() << r;e->accept();}private:QPointF m_topleft;qreal m_width = 100;qreal m_height = 100;QColor m_color = QColor(Qt::black);int m_lineWidth = 1;
};
#endif // SHAPE_H

#include "board.h"#include <QApplication>
#include "shape.h"
#include <QHBoxLayout>int main(int argc, char *argv[])
{QApplication a(argc, argv);ShapeImp* pImpl_circle = new Circle(QPointF(100,100),80);pImpl_circle->setFixedSize(300,300);Shape* pShape = new ShapeImpWin(pImpl_circle);pShape->setLineWidth(1);pShape->setLineColor(QColor(Qt::red));pShape->draw();pImpl_circle->show();ShapeImp* pImpl_rect = new Rectange(QPointF(10,10),80,80);pImpl_rect->setFixedSize(300,300);Shape* pShap1 = new ShapeImpWin(pImpl_rect);pShap1->setLineWidth(1);pShap1->setLineColor(QColor(Qt::red));pShap1->draw();pImpl_rect->show();return a.exec();
}