设计模式8——建造者模式

建造者模式定义一个具体的物体，是各种属性的集合。要创建该物体时，可以构建一个构造器，该构造器包含特定的构造方式，但是只提供一个接口，具体构造细节放在派生类中实现。

Builder.h内容

#ifndef Builder_H_H
#define Builder_H_H

#include <iostream>
#include <string>
#include <vector>
using namespace std;

class Product
{
public:
    Product() {}
    void display(){
        //cout << vecStr.size() << endl;
        for(size_t i=0; i<vecStr.size(); ++i){
            cout << vecStr[i] << "  ";
        }
        cout << endl;
    }
    void addItem(string str) { vecStr.push_back(str); }
private:
    vector<string> vecStr;
};

class Builder
{
public:
    Builder() {}
    virtual Product* getProduct() = 0;
    void Build(){
        buildItem1();
        buildItem2();
    }
    virtual void buildItem1() = 0;
    virtual void buildItem2() = 0;
    virtual ~Builder() {}
};


class BuilderOne : public Builder
{
public:
    BuilderOne() { product = new Product(); }
    virtual void buildItem1() { product->addItem("First"); }
    virtual void buildItem2() { product->addItem("Second"); }
    virtual Product* getProduct() { return product; }
    void release(){
        if(product != NULL){
            delete product;
            product = NULL;
        }
    }
    virtual ~BuilderOne() { release(); }
private:
    Product *product;
};

class BuilderTwo : public Builder
{
public:
    BuilderTwo() { product = new Product(); }
    virtual void buildItem1() { product->addItem("A"); }
    virtual void buildItem2() { product->addItem("B"); }
    virtual Product* getProduct() { return product; }
    void release(){
        if(product != NULL){
            delete product;
            product = NULL;
        }
    }
    virtual ~BuilderTwo() { release(); }
private:
    Product *product;
};

class Direct
{
public:
    Direct() : builder(NULL) {}
    void setBuilder(Builder *builder0){
        release();
        builder = builder0;
    }
    void Build(){
        builder->Build();
    }
    Product* getProduct() { return builder->getProduct(); }
    void release(){
        if(builder != NULL){
            delete builder;
            builder = NULL;
        }
    }
    ~Direct() { release(); }
private:
    Builder *builder;
};

void BuilderTest()
{
    Builder *builder1 = new BuilderOne();
    Builder *builder2 = new BuilderTwo();
    Direct *direct = new Direct();

    direct->setBuilder(builder1);
    direct->Build();
    direct->getProduct()->display();

    direct->setBuilder(builder2);
    direct->Build();
    direct->getProduct()->display();

    delete direct;
}

#endif

运行结果：