IsNew lets you test in OCL whether the current object has never been saved to the database; use it when a rule or expression must behave differently for newly created objects.
Syntax
self.isNew
The expression returns a Boolean value:
| Result | Meaning |
|---|---|
true
|
The object has never been saved to the database. |
false
|
The object has been saved to the database at least once. |
Example: Fruit
Assume that your model contains a class named Fruit.
Use the following expression when the current Fruit must be identified as new:
self.isNew
For a newly created Fruit that has not yet been saved, the expression evaluates to true. After that Fruit has been saved to the database, the same expression evaluates to false.
IsNew and IsDirty
Do not use IsNew to test whether an existing object was edited. An object can have been saved before and then changed afterwards; it is not new, but it is dirty. Use IsDirty to test whether an object has changed since its last save.
| Situation | self.isNew
|
IsDirty meaning |
|---|---|---|
A new Fruit has not been saved
|
true
|
Use IsDirty when you need to test for changes since the last save. |
An existing Fruit is changed after it was saved
|
false
|
The object has changed since its last save. |
An existing Fruit has no changes after its last save
|
false
|
The object has not changed since its last save. |
Use in an OCL expression
Enter the expression in the OCL Editor in the context of the class you want to test. For example, when the expression context is Fruit, use self.isNew to test that Fruit instance.
For an overview of available operators, see Documentation:OCL General Operators. For logical expressions that combine Boolean results, see Documentation:OCL Boolean Operators.