目录

Builder构建者模式：场景、功能、组成部分

场景

功能

组成部分：Builer+Director

---

Builder构建者模式：场景、功能、组成部分

场景

 还是老套路，首先不用设计模式来实现这个功能：

#include 
#include 
#include 
#include 
using namespace std;
 
template<class T>
string ConvertToString(T value) {
	stringstream ss;
	ss << value;
	return ss.str();
}
 
class ExportHeaderModel {
public:
	ExportHeaderModel(string strDepId, string strExportDate)
		:m_strDepId(strDepId), m_strExportDate(strExportDate)
	{}
	string getStrDepId() {
		return m_strDepId;
	}
	string getStrExportDate() {
		return m_strExportDate;
	}
private:
	string m_strDepId;//对账单的部门id
	string m_strExportDate;//对账单的导出日期
};
 
class ExportDataModel {
public:
	ExportDataModel(string strTransId,double Quantity)
		:m_strTransId(strTransId), m_Quantity(Quantity)
	{}
	string getStrTransId() { return m_strTransId; }
	double getQuantity() { return m_Quantity; }
private:
	string m_strTransId;//交易ID
	double m_Quantity;
};
 
class ExportFooterModel {
public:
	ExportFooterModel(string exportUser)
		:m_exportUser(exportUser)
	{}
	string getExportUser() {
		return m_exportUser;
	}
private:
	string m_exportUser;
};
 
//考虑一个周期，有多笔交易记录
class ExportToTextHelper {
public:
	void doExport(ExportHeaderModel& ehm, vectoredmCollection, ExportFooterModel& efm) {
		string strTemp = "";
 
		//第一步：写文件头
		strTemp += ehm.getStrDepId() + "," + ehm.getStrExportDate() + "\n";
		//第二部：写文件体数据
		for (auto it = edmCollection.begin(); it != edmCollection.end(); it++) {
			strTemp += (*it)->getStrTransId() + ":" + ConvertToString((*it)->getQuantity()) + "\n";
		}
		//第三步：拼接文件尾
		strTemp += efm.getExportUser() + "\n";
		cout << strTemp << endl;
	}
};
 
class ExportToXmlHelper {
public:
	void doExport(ExportHeaderModel& ehm, vectoredmCollection, ExportFooterModel& efm) {
		string strTemp = "";
 
		//第一步：拼接文件头
		strTemp.append("\n ");
		strTemp.append("\n");
		strTemp.append("    
\n");
		strTemp.append("        ");
		strTemp.append(ehm.getStrDepId() + "\n");
		strTemp.append("        " + ehm.getStrExportDate() + "\n");
		strTemp.append("    \n");
		//第二部：构建数据体
		strTemp.append("    \n");
		for (auto it = edmCollection.begin(); it != edmCollection.end(); it++) {
			strTemp.append("        " + (*it)->getStrTransId() + "\n");
			strTemp.append("        " + ConvertToString((*it)->getQuantity()) + "\n");
		}
		strTemp.append("    \n");
		//第三步：拼接文件尾
		strTemp.append("    
		strTemp.append("        " + efm.getExportUser() + "\n");
		strTemp.append("    \n\n");
 
		cout << strTemp << endl;
	}
};
 
int main() {
	ExportHeaderModel* pEhm = new ExportHeaderModel("南京1支行", "1st June");
 
	ExportDataModel* pEdm1 = new ExportDataModel("1", 10000.0f);
	ExportDataModel* pEdm2 = new ExportDataModel("2", 20000.0f);
	vectorVec;
	Vec.push_back(pEdm1);
	Vec.push_back(pEdm2);
	
	ExportFooterModel* pEfm = new ExportFooterModel("yxh");
 
	ExportToTextHelper helper1;
	helper1.doExport(*pEhm, Vec, *pEfm);
 
	ExportToXmlHelper helper2;
	helper2.doExport(*pEhm, Vec, *pEfm);
 
	return 0;
}

不错，但有一个问题，两种Helper中都存在着相同的步骤一二三。

既然都学了设计模式了，这种重复性的代码必然是不符合高逼格的，肯定要重构！

这里就引出了Builder模式

#include 
#include 
#include 
#include 
using namespace std;
 
template<class T>
string ConvertToString(T value) {
	stringstream ss;
	ss << value;
	return ss.str();
}
 
class ExportHeaderModel {
public:
	ExportHeaderModel(string strDepId, string strExportDate)
		:m_strDepId(strDepId), m_strExportDate(strExportDate)
	{}
	string getStrDepId() {
		return m_strDepId;
	}
	string getStrExportDate() {
		return m_strExportDate;
	}
private:
	string m_strDepId;//对账单的部门id
	string m_strExportDate;//对账单的导出日期
};
 
class ExportDataModel {
public:
	ExportDataModel(string strTransId, double Quantity)
		:m_strTransId(strTransId), m_Quantity(Quantity)
	{}
	string getStrTransId() { return m_strTransId; }
	double getQuantity() { return m_Quantity; }
private:
	string m_strTransId;//交易ID
	double m_Quantity;
};
 
class ExportFooterModel {
public:
	ExportFooterModel(string exportUser)
		:m_exportUser(exportUser)
	{}
	string getExportUser() {
		return m_exportUser;
	}
private:
	string m_exportUser;
};
 
//创建者模式
class Builder {
public:
	virtual void builderHeader(ExportHeaderModel& ehm) = 0;
	virtual void builderBody(vector& edmCollection) = 0;
	virtual void builderFoot(ExportFooterModel& efm) = 0;
	virtual string getResult() = 0;
protected:
	Builder() {}
};
 
class TextBuilder :public Builder {
public:
	void builderHeader(ExportHeaderModel& ehm) {
		m_strResult.append(ehm.getStrDepId() + "," + ehm.getStrExportDate() + "\n");
	}
	void builderBody(vector& edmCollection) {
		for (auto it = edmCollection.begin(); it != edmCollection.end(); it++) {
			m_strResult += (*it)->getStrTransId() + ":" + ConvertToString((*it)->getQuantity()) + "\n";
		}
	}
	void builderFoot(ExportFooterModel& efm) {
		m_strResult += efm.getExportUser() + "\n";
	}
	string getResult() {
		return m_strResult;
	}
public:
	TextBuilder() { m_strResult = ""; }
private:
	string m_strResult;
};
 
 
class Director {
public:
	Director(Builder* pBuilder) :m_pBuilder(pBuilder) {}
	void construct(ExportHeaderModel& ehm, vectoredmCollection, ExportFooterModel& efm) {
		m_pBuilder->builderHeader(ehm);
		m_pBuilder->builderBody(edmCollection);
		m_pBuilder->builderFoot(efm);
	}
private:
	Builder* m_pBuilder;
};
 
int main() {
	ExportHeaderModel* pEhm = new ExportHeaderModel("南京1支行", "1st June");
 
	ExportDataModel* pEdm1 = new ExportDataModel("1", 10000.0f);
	ExportDataModel* pEdm2 = new ExportDataModel("2", 20000.0f);
	vectorVec;
	Vec.push_back(pEdm1);
	Vec.push_back(pEdm2);
 
	ExportFooterModel* pEfm = new ExportFooterModel("yxh");
 
 
	Builder* pBuilder = new TextBuilder();
	Director* pDirector = new Director(pBuilder); 
	pDirector->construct(*pEhm, Vec, *pEfm);
	cout << pBuilder->getResult() << endl;
	return 0;
}

这里只重构了Text的创建。

其实总体看来，设计模式的目的就是：把不变的给客户，把以后可能变化的留给开发者，并且要便于开发者增加功能模块，要达到模块于模块之间的松耦合。

功能

• 构建复杂产品，而且是细化的，分步骤的构建产品，重在解决一步一步构造复杂对象的问题
• 这个构建过程是统一的，固定不变的，变化的部分就放到生成器Builder中
• 只要配置不同的Builder，那么同样的构建过程，就能构建出不同的产品出来

组成部分：Builer+Director

• Builder接口，定义如何构建各个部件，每个部件功能如何实现，如何装配这些部件到产品中去
• Director，定义如何组合来构建产品，负责整体的构建算法，通常分步骤来执行