依赖与构成的区别？ [英] Difference between dependency and composition?

问题描述

从这里获得的定义

依赖关系

更改类的结构或行为会影响其他相关的
类，那么这两个类之间有依赖关系。它需要
不一样反之亦然。

Change in structure or behaviour of a class affects the other related class, then there is a dependency between those two classes. It need not be the same vice-versa. When one class contains the other class it this happens.

组合

组合是聚合的一种特殊情况。在更具体的
方式中，限制聚合被称为组合。当对象
包含另一个对象时，如果包含的对象不存在
，而不存在容器对象，则称为
组合。

Composition is a special case of aggregation. In a more specific manner, a restricted aggregation is called composition. When an object contains the other object, if the contained object cannot exist without the existence of container object, then it is called composition.

Java中的具体示例来自这里和 here

Concrete examples in Java from here and here

依赖关系

class Employee {
    private Address address;

    // constructor 
    public Employee( Address newAddress ) {
        this.address = newAddress;
    }

    public Address getAddress() {
    return this.address;
    }
    public void setAddress( Address newAddress ) {
        this.address = newAddress;
    }
}

组合

final class Car {

  private final Engine engine;

  Car(EngineSpecs specs) {
    engine = new Engine(specs);
  }

  void move() {
    engine.work();
  }
}

推荐答案

差异可以在两个构造函数中看到：

The difference can be seen in the two constructors:

• 依赖关系：地址对象来自外部，它被分配到其他地方。这意味着地址和 Employee 对象单独存在，只有依赖

• Dependency: The Address object comes from outside, it's allocated somewhere else. This means that the Address and Employee objects exists separately, and only depend on each other.

组合：在这里你看到一个新的引擎被创建 Car 。 Engine 对象是 Car 的一部分。这意味着 Car 是 li>

Composition: Here you see that a new Engine is created inside Car. The Engine object is part of the Car. This means that a Car is composed of an Engine.

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