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This article introduces the relevant knowledge of "how to distinguish the relationship between UML class diagrams". In the operation of actual cases, many people will encounter such a dilemma, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

Distinguish several kinds of relations in UML class diagram

It is not easy to distinguish "association", "aggregation", "compostion" and "dependency" in UML class diagram.

1. Relationship (association):

1. The association relationship in the UML class diagram is the connection between classes, which makes one class know the properties and methods of another class.

2. The association can be two-way or one-way. A two-way association can have two arrows or no arrow, and an one-way association can have an arrow.

3. In Java or C++, associations are achieved by using member variables.

2. Aggregation relationship (aggregation):

1. The aggregation relation in the UML class diagram is a kind of association relationship, which is a strong association relationship.

2. Aggregation is the relationship between the whole and the parts. for example, a car is made up of engines, tires and other parts.

3. The aggregation relationship is also realized through member variables. However, the two classes involved in the association relationship are on the same level, while in the aggregation relationship, the two classes are on different levels, one representing the whole and the other representing the part.

4. Association and aggregation are indistinguishable only from the syntax of Java or C++, and the logical relationship between the classes involved must be examined.

3. Composite relationship (composition):

1. In the UML class diagram relation, the composite relation is a kind of association relation, which is stronger than the aggregation relation.

2. It requires that the object that represents the whole in the ordinary aggregation relationship is responsible for the life cycle of the object that represents the part.

4. Dependency (dependency):

1. The dependency relationship in UML class diagram is also the connection between classes.

2. Dependence is always one-way.

3. Dependency relationship is embodied as local variable, parameter of method or call to static method in Java or C++ language.

PublicclassPerson

{

Publicvoidbuy (Carcar)

{

...

}

}

5. Summary:

1. Different relationships in UML class diagrams use different UML legends.

2. For aggregation relations and composite relations, because they are all a kind of association relations, in the case of uncertainty, they can be described by association relations.

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