What is Association Relationship in Class Diagram?
In the next video, you will be introduced to the concept of an association relationship between classes.
In the previous video, you learnt about an association relationship between classes. An association relationship is also called a link or collaboration.
An association relationship is the general form of three other relationships. During the development of the system, you first identify which classes can be related to each other and draw a link or association relationship between them. Later, in the development process, you make decisions about the exact relationship between classes and refine the association relationship into one of the three relationships.
Association relationships are of two types:
- Unidirectional association: This is drawn using an arrow, which starts from the source class and points towards the target class. In a unidirectional association, objects of the source class can access the attributes and methods of objects of the target class. A unidirectional association relationship is labelled with an association name.
- Bidirectional association: This is drawn using a solid line. In bidirectional association, objects of both classes can access the attributes and methods of objects of the other class. A bidirectional association relationship is labelled with association end names.
Video Transcript
Association. Association is the generalized form of the three other relationship between the classes, namely aggregation, composition and generalization. Association represents any collaboration between the two classes. We will now briefly see more about association with an example. Here an inventory manager interacts with an order class. Here, the inventory manager actually creates an order. If you see this relationship is an association between inventory manager and order and association relationships are generally labeled. It can be both unidirectional or bi directional. When I say unidirectional, only inventory manager can create an order and not vice versa. In the next example, the relationship between admin and inventory manager is bi directional, meaning an Admin assigns tasks to an inventory manager, an inventory manager reports to admin. So there is a collaboration between admin and inventory manager and it is bi directional.
Video Recap
Association is a generalized form of the three relationships between classes - aggregation, composition, and generalization.
Association represents any collaboration between two classes and can be labeled as unidirectional or bi-directional.
An example of association is the interaction between an inventory manager and an order class.
The relationship between an admin and an inventory manager is bi-directional, involving collaboration and task assignment.
In the next video, you will see how to represent multiplicity in an association relationship and what the different types of multiplicities are.
In the previous video, you learnt about multiplicity, which can be of three types:
- One-to-one
- One-to-many
- Many-to-many
Whenever you draw an association relationship between two classes, you should always show the multiplicity for those classes across that association relationship.
In the next video, you will see how to draw an association relationship between classes in draw.io.
In the previous video, you saw how to draw an association relationship between classes in a Class Diagram.
Through this segment, you were introduced to the concept of association between classes and how it is represented in Class Diagrams.