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Class Content

A class can contain any of the following items. Interfaces are limited to those indicated as [Allowed in interfaces]. A trait can contain most of the items, indicated as indicated as [Allowed in traits].

• Comments describe the intent of your class (or interface), and any other elements in the class.[Allowed in interfaces] [Allowed in traits]


• isA directives that specify a superclass to your class (e.g. a Supervisor could be described as "isA Person"). A class can only have one isA clause referring to another class, but can have many referring to traits or interfaces. [More than one allowed in interfaces] [More than one allowed in traits]


• An abstract; keyword, specifying that the class is abstract (cannot be instantiated, must have at least one concrete subclass).


• Depend directives that describe external dependencies that might be used by your class within methods [Allowed in interfaces] [Allowed in traits].


• Attributes describing simple data that can be found in any element of the class (i.e. name, dob, amount) [Allowed in traits]. These can be preceded by the keyword const to declare constants.


• Inline associations that define links to instances of other classes (or to other instances of this class). [Allowed in traits] (can also be specified outside classes)


• Methods that provide behaviour for the class. [Allowed in interfaces, but with no method body] [Allowed in traits] (state events are also methods, and methods can also be specified in states)


• Enumerations for use inside this class (can also be specified outside classes)


• State machine definitions that describe declaratively attributes that change value in certain behaviour patterns in response to actions such as method calls. [Allowed in traits]


• A singleton directive that limits the system to only one instance of this class (e.g. there may only be one Bank in a banking system)[Allowed in traits]


• An immutable directive that ensures that once constructed, an instance cannot be modified (under development).[Allowed in traits]


• Key directives indicating which attributes (or in the future, associations) are going to be used to define when one element is equal to another.[Allowed in traits]


• Generation templates and emit methods for generating string output.


• Invariant constraints. These are Boolean expressions that limit the values of attributes and other elements. [Allowed in traits] (other types of constraints can be specified in methods)


• Mixset definitions that are named blocks containing any of the other items that can appear in classes (i.e. those listed on this page). These allow for conditional compilation because the content of the mixset an either be active or not active. Mixsets are activated by use statements or command line arguments.[Allowed in traits]


• Class definitions nested inside this class that define subclass of this class as an alternative to using the isA clause. (these are not inner classes; those are defined as below)


• Trace directives to direct generation of traces from the code. [Allowed in traits]


• An inner class, specified either by the keyword inner or static, followed by a class definition. These are only relevant to Java generation.


• Several other items to be documented later including the ability to colour classes in diagrams, and to specify test cases.