The following are several general representation methods. There is a unified detailed representation in the process of use. The meaning of the detailed symbols in the class diagram The following UML diagram shows the relationship of various class diagrams more vividly:ģ. Generalization = Implementation> Composition> Aggregation> Association> Dependence The order of strength of various relationships: : A dotted line with an arrow pointing to the user : Local variables, method parameters or calls to static methods : It is a relationship of use, that is, the implementation of one class needs the assistance of another class, so try not to use two-way interdependence. : A solid line with a solid diamond, the diamond pointing to the whole It requires the object representing the whole in the ordinary aggregation relationship to be responsible for the life cycle of the object representing the part. The composition relationship is a kind of association relationship, which is stronger than the aggregation relationship. If a company and a department are in a whole and part relationship, there is no department without a company. : It is the relationship between the whole and the part, but the part cannot exist separately from the whole. : A solid line with a hollow diamond, the diamond pointing to the whole If the car and the tire are in a whole and part relationship, the tire can still exist without the car.Īggregation relationship is a kind of association relationship, which is a strong association relationship association and aggregation cannot be distinguished grammatically, and specific logical relationships must be examined. : It is the relationship between the whole and the part, and the part can exist separately from the whole. The following picture shows its own association: The course is an abstract thing and he does not own students. A student may have to take multiple courses.
But the relationship between a student and a course is one-way. The teacher has multiple students, and the students may have multiple teachers.
In the picture above, the teacher and the student are in a two-way relationship. 【Arrow and Pointing】: A solid line with an ordinary arrow pointing to the owner Two-way associations can have two arrows or no arrows, and one-way associations have one arrow. : It is a relationship of ownership, which enables one class to know the attributes and methods of another class for example, the relationship between teacher and student, husband and wife can be two-way or one-way. : A dotted line with a triangular arrow, the arrow points to the interface : A relationship between a class and an interface, which means that the class is the realization of all the characteristics and behaviors of the interface. : A solid line with a triangular arrow, the arrow points to the parent category For example: Tiger is a kind of animal, which has the characteristics of tiger and the commonality of animals. It specifies how the subclass specializes all the characteristics and behaviors of the parent class. : It is an inheritance relationship that represents the general and special relationship. In UML class diagrams, there are several common relationships: Generalization, Realization, Association, Aggregation, Composition, Dependency
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