[TS Design Patterns] 행동 패턴 - 전략

Strategy

- 알고리즘들의 패밀리를 정의하고, 각 패밀리를 별도의 클래스에 넣은 후 그들의 객체들을 상호교환할 수 있도록 함

- 행동들의 객체들을 객체들로 변환하며 이들이 원래 콘텍스트 객체 내에서 상호 교환이 기능하게 만들어 줌

- 원래 객체는 콘텍스트라고 불리며 전략 객체에 대한 참조를 포함함

- 콘텍스트는 행동의 실행을 연결된 전략 객체에 위임함

- 콘텍스트와 작업을 수행하는 방식을 변경하기 위해 다른 객체들은 현재 연결된 전략 객체를 다른 전략 객체와 대체 가능

- 다양한 프레임워크에서 사용자들이 클래스를 확장하지 않고 클래스의 행동을 변경할 수 있도록 자주 사용됨

 

- 예시

 

/**
 * The Context defines the interface of interest to clients.
 */
class Context {
  /**
   * @type {Strategy} The Context maintains a reference to one of the Strategy
   * objects. The Context does not know the concrete class of a strategy. It
   * should work with all strategies via the Strategy interface.
   */
  private strategy: Strategy;

  /**
   * Usually, the Context accepts a strategy through the constructor, but also
   * provides a setter to change it at runtime.
   */
  constructor(strategy: Strategy) {
    this.strategy = strategy;
  }

  /**
   * Usually, the Context allows replacing a Strategy object at runtime.
   */
  public setStrategy(strategy: Strategy) {
    this.strategy = strategy;
  }

  /**
   * The Context delegates some work to the Strategy object instead of
   * implementing multiple versions of the algorithm on its own.
   */
  public doSomeBusinessLogic(): void {
    // ...

    console.log(
      "Context: Sorting data using the strategy (not sure how it'll do it)"
    );
    const result = this.strategy.doAlgorithm(['a', 'b', 'c', 'd', 'e']);
    console.log(result.join(','));

    // ...
  }
}

/**
 * The Strategy interface declares operations common to all supported versions
 * of some algorithm.
 *
 * The Context uses this interface to call the algorithm defined by Concrete
 * Strategies.
 */
interface Strategy {
  doAlgorithm(data: string[]): string[];
}

/**
 * Concrete Strategies implement the algorithm while following the base Strategy
 * interface. The interface makes them interchangeable in the Context.
 */
class ConcreteStrategyA implements Strategy {
  public doAlgorithm(data: string[]): string[] {
    return data.sort();
  }
}

class ConcreteStrategyB implements Strategy {
  public doAlgorithm(data: string[]): string[] {
    return data.reverse();
  }
}

/**
 * The client code picks a concrete strategy and passes it to the context. The
 * client should be aware of the differences between strategies in order to make
 * the right choice.
 */
const context = new Context(new ConcreteStrategyA());
console.log('Client: Strategy is set to normal sorting.');
context.doSomeBusinessLogic();

console.log('');

console.log('Client: Strategy is set to reverse sorting.');
context.setStrategy(new ConcreteStrategyB());
context.doSomeBusinessLogic();

 

- 활용

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[아티클]

[TS 사용 예시]