设计模式(3)-策略模式(Strategy) (一)

【描述】策略模式本质上利用的是面向对象的多态特性，构建者不必自身包含实现的逻辑，而是根据需要利用其他对象中的算法。

【UML图】

图1 UML图

(1) 定义了一个Methods基类，包含一个策略的接口MethodsInterface。

(2) 定义了MethodsStrategyA、MethodsStrategyB两种策略。

(3) 定义了一个策略构建者Context，包含ContextInterface方法。

【示例代码】

methods.h

[html]
#ifndef METHODS_H
#define METHODS_H

class Methods
{
public:
Methods();

public:
virtual void MethodsInterface();
};

#endif // METHODS_H
#ifndef METHODS_H
#define METHODS_H

class Methods
{
public:
Methods();

public:
virtual void MethodsInterface();
};

#endif // METHODS_H

methods.cpp

[html]
#include
#include "methods.h"

Methods::Methods()
{
qDebug()<<"construct Methods";
}

void Methods::MethodsInterface()
{
qDebug()<<"Methods::MethodsInterface";
}
#include
#include "methods.h"

Methods::Methods()
{
qDebug()<<"construct Methods";
}

void Methods::MethodsInterface()
{
qDebug()<<"Methods::MethodsInterface";
}

methodstrategya.h

[html]
#ifndef METHODSTRATEGYA_H
#define METHODSTRATEGYA_H

#include "methods.h"

class MethodStrategyA : public Methods
{
public:
MethodStrategyA();

public:
void MethodsInterface();
};

#endif // METHODSTRATEGYA_H
#ifndef METHODSTRATEGYA_H
#define METHODSTRATEGYA_H

#include "methods.h"

class MethodStrategyA : public Methods
{
public:
MethodStrategyA();

public:
void MethodsInterface();
};

#endif // METHODSTRATEGYA_H

methodstrategya.cpp

[html]
#include
#include "methodstrategya.h"

MethodStrategyA::MethodStrategyA()
{
qDebug()<<"construct MethodStrategyA";
}

void MethodStrategyA::MethodsInterface()
{
qDebug()<<"Strategy A";
}
#include
#include "methodstrategya.h"

MethodStrategyA::MethodStrategyA()
{
qDebug()<<"construct MethodStrategyA";
}

void MethodStrategyA::MethodsInterface()
{
qDebug()<<"Strategy A";
}

methodstrategyb.h

[html]
#ifndef METHODSTRATEGYB_H
#define METHODSTRATEGYB_H

#include "methods.h"

class MethodStrategyB : public Methods
{
public:
MethodStrategyB();

public:
void MethodsInterface();
};

#endif // METHODSTRATEGYB_H
#ifndef METHODSTRATEGYB_H
#define METHODSTRATEGYB_H

#include "methods.h"

class MethodStrategyB : public Methods
{
public:
MethodStrategyB();

public:
void MethodsInterface();
};

#endif // METHODSTRATEGYB_H

methodstrategyb.cpp

[html] ‘
#include
#include "methodstrategyb.h"

MethodStrategyB::MethodStrategyB()
{
qDebug()<<"construct MethodStrategyB";
}

void MethodStrategyB::MethodsInterface()
{
qDebug()<<"Strategy B";
}
#include
#include "methodstrategyb.h"

MethodStrategyB::MethodStrategyB()
{
qDebug()<<"construct MethodStrategyB";
}

void MethodStrategyB::MethodsInterface()
{
qDebug()<<"Strategy B";
}

context.h

[html]
#ifndef CONTEXT_H
#define CONTEXT_H

#include "methods.h"

class Context
{
public:
Context(Methods *method);

private:
Methods *_method;

public:
void ContextInterface();
};

#endif // CONTEXT_H
#ifndef CONTEXT_H
#define CONTEXT_H

#include "methods.h"

class Context
{
public:
Context(Methods *method);

private:
Methods *_method;

public:
void ContextInterface();
};

#endif // CONTEXT_H

context.cpp

[html]
#include "context.h"

Context::Context(Methods *method)
{
_method = method;
}

void Context::ContextInterface()
{
_method->MethodsInterface();
}
#include "context.h"

Context::Context(Methods *method)
{
_method = method;
}

void Context::ContextInterface()
{
_method->MethodsInterface();
}

main.cpp

[html]
#include
#include "context.h"
#include "methods.h"
#include "methodstrategya.h"
#include "methods