Home Backend Development C#.Net Tutorial A brief introduction to strategy pattern in C++ design patterns

A brief introduction to strategy pattern in C++ design patterns

Jan 18, 2017 pm 03:05 PM

Strategy pattern definition:

defines a family of algorithms and encapsulates them separately so that they can be replaced with each other. This pattern allows changes in the algorithm to not affect the customers who use the algorithm.

Strategy pattern includes the following roles:

Context: Environment class

Strategy: Abstract strategy class

ConcreteStrategy: Concrete strategy class

UML class diagram:

A brief introduction to strategy pattern in C++ design patterns

Test case

[code]int main(){
    //商品费用
    double cost;
    //采取某种收费策略之后的费用
    double result;
    //假如
    cost = 1029.88;

    //声明要使用的具体策略类
    //这里显示出了策略类的缺点:客户端必须知道有哪些具体封装的算法。如本例必须知道三种收费方式Normal、Return、Rebate。
    StrategyCashSuper *Normal = new ConerectStrategyNormal(cost);//抽象策略类(基类)指针指向派生类->具体策略类(普通收费方式)
    StrategyCashSuper *Return = new ConerectStrategyReturn(cost); //满300返100收费方式
    StrategyCashSuper *Rebate = new ConerectStrategyRebate(cost); //打八折收费
    //声明环境类,具体调用的算法,由它来维护
    Context *c = new Context();
    //设置使用的策略类
    c->setStrategy(Normal);//设置为普通收费
    //调用算法
    result = c->getChargeResult();
    std::cout << "Accrued expenses: " << result << std::endl;

    c->setStrategy(Return);//设置为满300返100收费方式
    //调用算法
    result = c->getChargeResult();
    std::cout << "Accrued expenses: " << result << std::endl;

    c->setStrategy(Rebate);//设置为打八折收费
    //调用算法
    result = c->getChargeResult();
    std::cout << "Accrued expenses: " << result << std::endl;

    return 0;
}
Copy after login

Header file Strategy.h

[code]#ifndef _2STRATEGY_H_
#define _2STRATEGY_H_
//策略类,算法基类
class StrategyCashSuper{
protected:
    //商品应付费用,定义为保护成员供子类继承
    double cost;   
public:
    //构造函数
    StrategyCashSuper(double c):cost(c){}
    //收费结果算法
    virtual double ChargeResult();//本想定义为纯虚函数,但不可以。因为虚基类本不能实例化
};

//正常收费算法
class ConerectStrategyNormal: public StrategyCashSuper{
public:
    //构造函数
    ConerectStrategyNormal(double c):StrategyCashSuper(c){}
    //根据本类的收费方式,重写继承的收费算法
    double ChargeResult()override;
};

//满300返100收费算法
class ConerectStrategyReturn: public StrategyCashSuper{
public:
    //构造函数
    ConerectStrategyReturn(double c):StrategyCashSuper(c){}
    //重写收费算法
    double ChargeResult()override;    
};

//打八折收费算法
class ConerectStrategyRebate: public StrategyCashSuper{
public:
    //构造函数
    ConerectStrategyRebate(double c):StrategyCashSuper(c){}
    //重写收费算法
    double ChargeResult()override;  

};

//环境类,根据具体算法,维护上下文使用的类
class Context{
private:
    //策略基类
    StrategyCashSuper *SCS;
public:
    //设置使用的策略
    void setStrategy(StrategyCashSuper *s);
    //具体执行的算法
    double getChargeResult();
};

#endif
Copy after login

Implementing Strategy.cpp

[code]#include "2Strategy.h"
//基类
double StrategyCashSuper::ChargeResult(){
    return 0;
}

//正常收费
double ConerectStrategyNormal::ChargeResult(){
    return cost;
}

//满300返100收费算法
double ConerectStrategyReturn::ChargeResult(){
    double res = cost;
    if(res >= 300)
        res = cost - 100;
    return res;
}
//打八折收费算法
double ConerectStrategyRebate::ChargeResult(){
    return cost *0.8;
}

//设置使用的算法
void Context::setStrategy(StrategyCashSuper *s){
    SCS = s;
}

//具体执行的算法
double Context::getChargeResult(){
    return SCS->ChargeResult();
}
Copy after login

Summary:

The strategy pattern allows the algorithm to change independently of the clients using it, also becoming the policy pattern. Strategy pattern is an object behavior pattern.

The strategy pattern contains 3 roles: the abstract strategy class declares abstract methods for the supported algorithms and is the parent class of all strategy classes; the concrete strategy class implements the algorithm defined in the abstract strategy class. The environment class can use multiple strategy classes to solve a certain problem (the disadvantage is that the client needs to know all the encapsulated strategy classes), and maintain a reference instance to the abstract strategy class in the environment class.

The strategy pattern is an encapsulation of the algorithm. It separates the responsibility of the algorithm from the algorithm itself and delegates it to different object management. The strategy pattern usually encapsulates a series of algorithms into a series of strategy classes, as a subclass of an abstract strategy class.

The main advantage of the strategy mode is its perfect support for the "opening and closing principle". Algorithms can be replaced or new algorithms can be added without modifying the original system. It manages the algorithm family very well and improves the reusability of the code. , is an implementation method that replaces inheritance and avoids multiple conditional transfer statements; its disadvantage is that the client must know all the policy classes and understand their differences. At the same time, it increases the number of classes in the system to a certain extent, and there may be Lots of strategy classes.

Applicable situations of the strategy pattern include: there are many classes in a system, and the difference between them is only their behavior. Using the strategy pattern can dynamically let an object choose one behavior among many behaviors; a system needs to dynamically Choose one of several algorithms; avoid using multiple conditional selection statements that are difficult to maintain; hope to encapsulate the algorithm and its related data structures in a specific strategy class.

The above is the content of the strategy pattern of C++ design pattern. For more related content, please pay attention to the PHP Chinese website (www.php.cn)!


Statement of this Website
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn

Hot AI Tools

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress AI Tool

Undress images for free

Clothoff.io

Clothoff.io

AI clothes remover

Video Face Swap

Video Face Swap

Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Tools

Notepad++7.3.1

Notepad++7.3.1

Easy-to-use and free code editor

SublimeText3 Chinese version

SublimeText3 Chinese version

Chinese version, very easy to use

Zend Studio 13.0.1

Zend Studio 13.0.1

Powerful PHP integrated development environment

Dreamweaver CS6

Dreamweaver CS6

Visual web development tools

SublimeText3 Mac version

SublimeText3 Mac version

God-level code editing software (SublimeText3)

What is the role of char in C strings What is the role of char in C strings Apr 03, 2025 pm 03:15 PM

In C, the char type is used in strings: 1. Store a single character; 2. Use an array to represent a string and end with a null terminator; 3. Operate through a string operation function; 4. Read or output a string from the keyboard.

Four ways to implement multithreading in C language Four ways to implement multithreading in C language Apr 03, 2025 pm 03:00 PM

Multithreading in the language can greatly improve program efficiency. There are four main ways to implement multithreading in C language: Create independent processes: Create multiple independently running processes, each process has its own memory space. Pseudo-multithreading: Create multiple execution streams in a process that share the same memory space and execute alternately. Multi-threaded library: Use multi-threaded libraries such as pthreads to create and manage threads, providing rich thread operation functions. Coroutine: A lightweight multi-threaded implementation that divides tasks into small subtasks and executes them in turn.

How to calculate c-subscript 3 subscript 5 c-subscript 3 subscript 5 algorithm tutorial How to calculate c-subscript 3 subscript 5 c-subscript 3 subscript 5 algorithm tutorial Apr 03, 2025 pm 10:33 PM

The calculation of C35 is essentially combinatorial mathematics, representing the number of combinations selected from 3 of 5 elements. The calculation formula is C53 = 5! / (3! * 2!), which can be directly calculated by loops to improve efficiency and avoid overflow. In addition, understanding the nature of combinations and mastering efficient calculation methods is crucial to solving many problems in the fields of probability statistics, cryptography, algorithm design, etc.

distinct function usage distance function c usage tutorial distinct function usage distance function c usage tutorial Apr 03, 2025 pm 10:27 PM

std::unique removes adjacent duplicate elements in the container and moves them to the end, returning an iterator pointing to the first duplicate element. std::distance calculates the distance between two iterators, that is, the number of elements they point to. These two functions are useful for optimizing code and improving efficiency, but there are also some pitfalls to be paid attention to, such as: std::unique only deals with adjacent duplicate elements. std::distance is less efficient when dealing with non-random access iterators. By mastering these features and best practices, you can fully utilize the power of these two functions.

How to apply snake nomenclature in C language? How to apply snake nomenclature in C language? Apr 03, 2025 pm 01:03 PM

In C language, snake nomenclature is a coding style convention, which uses underscores to connect multiple words to form variable names or function names to enhance readability. Although it won't affect compilation and operation, lengthy naming, IDE support issues, and historical baggage need to be considered.

Usage of releasesemaphore in C Usage of releasesemaphore in C Apr 04, 2025 am 07:54 AM

The release_semaphore function in C is used to release the obtained semaphore so that other threads or processes can access shared resources. It increases the semaphore count by 1, allowing the blocking thread to continue execution.

Issues with Dev-C version Issues with Dev-C version Apr 03, 2025 pm 07:33 PM

Dev-C 4.9.9.2 Compilation Errors and Solutions When compiling programs in Windows 11 system using Dev-C 4.9.9.2, the compiler record pane may display the following error message: gcc.exe:internalerror:aborted(programcollect2)pleasesubmitafullbugreport.seeforinstructions. Although the final "compilation is successful", the actual program cannot run and an error message "original code archive cannot be compiled" pops up. This is usually because the linker collects

C   and System Programming: Low-Level Control and Hardware Interaction C and System Programming: Low-Level Control and Hardware Interaction Apr 06, 2025 am 12:06 AM

C is suitable for system programming and hardware interaction because it provides control capabilities close to hardware and powerful features of object-oriented programming. 1)C Through low-level features such as pointer, memory management and bit operation, efficient system-level operation can be achieved. 2) Hardware interaction is implemented through device drivers, and C can write these drivers to handle communication with hardware devices.

See all articles