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oopumlclass-designclass-diagram
ThisaruG
ThisaruG

Reputation: 3412

Class diagram - multiple classes uses same class

I am designing a class diagram for an assignment. In this design, I use a separate class called Currency, to define currency values and their functionality. there are at least four other classes have to use this Currency class.

Upvotes: 2

Views: 2605

Answers (1)

Ister
Ister

Reputation: 6318

There is nothing wrong and a reusability of a class is valuable. Actually that's a standard situation.

If you use this class in another class as an attribute you have two options to depict that:

  1. draw an association relationship (line) from the class using to the class that is used.
  2. put the attribute in a proper compartment of a class that is using and as a type of an attribute (after a colon) put the name of the used class.

The benefit of the first approach is that you immediately see the dependency between the classes.

If you use a class but not directly as an attribute type you use other relationship types that suit best to the situation you want to describe.

As I imagine one of your concerns is that you'll have a lot of relationships pointing to your class (in your case Currency). Don't worry about that. You don't have to put everything in a single diagram. Put a full specification of your class on one diagram with those relationships where it uses something else and then put only the class box with a name (without any compartment) on diagrams defining those elements that use your class. It will make your model readable. And with a support of some CASE tool you will be able to see all relationship and dependencies of this class anyway. By the way that's how the UML specification is written. Look for example how Namespace is used in the diagrams there (and many others as well).

Of course I'm not suggesting creating one diagram per one element to define it. No. Collect them in logical Packages (hey - that's exactly what Packages are for!) and make a class diagram per Package. If the Package becomes too large - you might need to split it into smaller subpackages.

For Currency your Package would be probably something like Utils. It can also contain other elements like Date, Address etc. Note - these are typical examples, probably every analyst/designer/programmer sooner or later has to cope with those elements. If you build them well, you'll be really able to reuse them in future applications as well.

One last thought. While you build "package based" Class diagram you might also need a diagram that shows just specific parts coming from several Packages to clarify some bit of your system/business/whatsoever. This is also absolutely fine. Again a benefit of CASE tool here is that it keeps consistency in your model.

Upvotes: 5

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