I am drawing a class diagram of a rational number calculator program that I've created and I have a question about the relationship between some of the classes - the program has been completed so the class diagram has to reflect the finished version, (even though you may not agree with the design I have a question about the UML notation I should use)
the question is:
if the top level class (e.g. I named it Calculator) has an instance of a Stacks class (a class written that uses a Stack interface and the pop, peek methods are written to push nodes (an inner private class in the Stacks class ) and and then this stack instance (which was instantiated in Calculator class ) is placed as an input parameter to another class's method for e.g. an object of CalcIOConsole class is in the Calculator class and invokes a method to display the stack, is there an association between the CalcIOConsole class and the Stacks class (i.e should a line be drawn between these two classes, or only from the Calculator class to the Stacks class?)
At the moment I have a weak aggregration from the Calculator class to the StacksInterface class. (the Stacks class created implements the StacksInt interface and the object is instantiated as a StackInt object with new Stacks<Rational>();
the rational class is instantiated in the Calculator class as well, (the numbers are stored as Rational objects from a Rational class which has a nominator/demoniator). if a rational object is instantiated or returned by a method in the CalcIOConsole class does it have a direct association with the rational class?
At the moment I have :
CalcIOConsole--------->>Ca
>> means implements
<----- means depends on
______> means association
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by: KelvinYPosted on 2007-04-23 at 15:19:17ID: 18961960
Hi akpp,
From your description it sounds like there is no relationship between the CalcIOConsole class and the Stacks class. Neither class is contained in the other through inheritance or composition. The methods that interact with the CalcIOConsole class and the Stacks class are both contained within the Calculator class, so Calculator is the class that would have a relationship with the other two.
A class that contains methods that return a certain type does not necessarily have a relationship with the returned type unless you actually have a member of the calling class that is of that type. So, for instance, if your Calculator implements a stack object that contains an aggregation of Rational objects then there is a relationship between the stack class (StackInt) and the Rational class (and between the Calculator class and the StackInt class).
Regards,
KelvinY