@Retention(RetentionPolicy.RUNTIME) @Target({ElementType.CONSTRUCTOR, ElementType.METHOD}) @Incubating @Postcondition @Repeatable(EnsuresConditions.class) @AnnotationProcessorImplementation(EnsuresAnnotationProcessor.class) public @interface Ensures
Represents a method postcondition.
A postcondition is a condition that is guaranteed to be fulfilled by suppliers.
A method's postcondition is executed after a method call has finished. A successor's postcondition strengthens the postcondition of its parent class, e.g. if A.someMethod declares a postcondition and B.someMethod overrides the method the postconditions are combined with a boolean AND.
Compared to pre-conditions, postcondition annotation closures are optionally called with two additional closure arguments: result and old.
result is available if the corresponding method has a non-void return-type and holds the result of the method call. Be aware that modifying the internal state of a reference type can lead to side-effects. Groovy-contracts does not keep track of any sort of modifications, neither any conversion to immutability.
old is available in every postcondition. It is a Map which holds the values of value types and Cloneable types before the method has been executed.
Examples:
Accessing the result closure parameter:
@Ensures({ result -> result != argument1 })
def T someOperation(def argument1, def argument2) {
...
}
Accessing the old closure parameter:
@Ensures({ old -> old.counter + 1 == counter })
def T someOperation(def argument1, def argument2) {
...
}