UML Weekend Crash Course™ - To Parent Directory

Session 9—Modeling the Static View: The Class Diagram 99
Return data type: Required for a return value, but return values are optional. The
UML only allows for the type, not the name, which is consistent with most programming
languages. There may only be one return data type, which again is consistent
with most programming languages.
Visibility (+, -, #, ~): Required before code generation. The visibility values are
defined by the programming language, but typically include public (+), private (-),
protected (#), and package (~).
Class level operation (underlined operation declaration): Optional. Denoted as
an operation accessible at the class level; requires an instance (object) reference.
Argument name: Required for each parameter, but parameters are optional. Any
number of arguments is allowed.
Argument data type: Required for each parameter, but parameters are optional.
Constraints: Optional. In general, constraints express rules that must be enforced
in the execution of the operation. In the case of parameters, they express criteria
that the values must satisfy before they may be used by the operation. You can
think of them as operation level pre-conditions.
Creating an operation specification
Table 9-2 shows you how to create a sample operation to determine the total amount due on
an order. The total is the sum of all line items less the volume discount. Each line item
amount is the product of the unit price and discount. You need the answer back as a dollar
amount.
Table 9-2
Creating an Operation Specification
Operation Element Description
Name the operation.
Define the arguments/parameters:
All the input information is on the Order object,
so an instance of Order is the only argument.
Name the argument and data type and separate
them with a colon. Try to use argument names
that match the argument type; this makes
referring to the value within the method
easier. The data type in this example is the
user-defined class “Order.” Enclose the
arguments in parentheses.
Operation Element Example
totalOrderAmount
totalOrderAmount (order : Order)
Continued