You can define one value on a class by giving an attribute a name, a simple type, and, when needed, a nullable marker; this page is for people defining class information in MDriven.
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Write an attribute signature
An attribute holds one simple value for each object of a class. Write its name and type together in this form:
AttributeName:Type
For example:
SomeName:String
In this example, SomeName is the attribute name and String is the simple value type.
Allow an empty value
Add a question mark after the type when the attribute may have no assigned value:
SomeName:String?
The ? means the attribute is nullable. Nullable is different from a value such as zero. For an integer attribute, zero is an assigned value; a nullable integer can instead have no value assigned.
| Signature | Meaning |
|---|---|
SomeName:String
|
SomeName has the simple type String.
|
SomeName:String?
|
SomeName has the simple type String and may have no assigned value.
|
Choose how the attribute is stored
Attributes are normally persistent: their values are saved. You can also use a non-persistent attribute when its value should exist only in memory.
For example, use a persistent attribute for information that must be retained. Use a non-persistent attribute for information that is only needed while the object is in memory.
Use a derived attribute for a calculated value
You can set an attribute's mode to derived when its value is calculated from other values rather than maintained as an independently entered value.
For example, if one value is calculated from other attributes, mark that calculated attribute as derived so the model expresses that it depends on those values.
Use an attribute or an association
Use an attribute for one simple value, such as a string. To represent a relationship to another class or a list of values, use an association instead.
Check the model
After adding or changing an attribute, use validation and resolve errors before you start the Prototyper or deploy the model.