The UML Class diagram is a graphical notation used to construct and visualize object oriented systems. A class diagram in the Unified Modeling Language UML is a type of static structure diagram that describes the structure of a system by showing the system's:. A Class is a blueprint for an object. Objects and classes go hand in hand. We can't talk about one without talking about the other. And the entire point of Object-Oriented Design is not about objects, it's about classes, because we use classes to create objects.
So a class describes what an object will be, but it isn't the object itself. In fact, classes describe the type of objects, while objects are usable instances of classes. Each Object was built from the same set of blueprints and therefore contains the same components properties and methods. The standard meaning is that an object is an instance of a class and object - Objects have states and behaviors. A dog has states - color, name, breed as well as behaviors -wagging, barking, eating. An object is an instance of a class.
A class represent a concept which encapsulates state attributes and behavior operations. Each attribute has a type. Each operation has a signature. The class name is the only mandatory information. Each parameter in an operation method may be denoted as in, out or inout which specifies its direction with respect to the caller.
This directionality is shown before the parameter name. The choice of perspective depends on how far along you are in the development process. During the formulation of a domain model , for example, you would seldom move past the conceptual perspective. Analysis models will typically feature a mix of conceptual and specification perspectives.
Design model development will typically start with heavy emphasis on the specification perspective , and evolve into the implementation perspective. The perspective affects the amount of detail to be supplied and the kinds of relationships worth presenting. As we mentioned above, the class name is the only mandatory information. UML is not just about pretty pictures. If used correctly, UML precisely conveys how code should be implemented from diagrams.
