Interaction between design patterns and the Standard Template Library (STL) in C++

Design patterns are used in conjunction with STL to create more flexible, reusable, and maintainable code. By combining STL (providing basic data structures and algorithms) and design patterns (providing a framework for organizing code), such as the observer pattern and practical examples of lists, observers can be added and removed dynamically, thereby improving the flexibility and reusability of the code. .

Interaction between design patterns and STL in C

Design patterns are a collection of reusable solutions in software engineering, while standards The Template Library (STL) is a powerful container and algorithm library in C.

Why use design patterns with STL?

By using design patterns with STL, you can create more flexible, reusable, and maintainable code. STL provides basic data structures and algorithms, while design patterns provide a framework for organizing and structuring code.

Practical Case: Observer Pattern and Lists

Consider a practical case of the Observer pattern, where multiple observers can subscribe to a topic and receive notifications of topic status changes . We can use STL lists to manage observers:

#include <list>
#include <iostream>

using namespace std;

class Subject {
public:
    void attach(Observer* observer) { observers_.push_back(observer); }
    void detach(Observer* observer) { observers_.remove(observer); }
    void notify() {
        for (auto& observer : observers_) {
            observer->update();
        }
    }

private:
    list<Observer*> observers_;
};

class Observer {
public:
    virtual void update() = 0;
};

class ConcreteObserverA : public Observer {
public:
    void update() { cout << "ConcreteObserverA notified.\n"; }
};

class ConcreteObserverB : public Observer {
public:
    void update() { cout << "ConcreteObserverB notified.\n"; }
};

int main() {
    Subject subject;
    ConcreteObserverA observerA;
    ConcreteObserverB observerB;

    subject.attach(&observerA);
    subject.attach(&observerB);
    subject.notify();

    return 0;
}

Benefits

• Using STL lists to manage observers provides underlying storage and access functions.
• The combination of the Observer pattern and STL lists allows dynamic addition and removal of observers.
• This makes the code more flexible and reusable.

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