Method annotation that creates a cache for the results of the execution of the annotated method. Whenever the method is called, the mapping between the parameters and the return value is preserved in a cache making subsequent calls with the same arguments fast.

Example usage:

 class MemoizedExample {
 
     @Memoized
     int sum(int n1, int n2) {
         println "$n1 + $n2 = ${n1 + n2}" 
         n1 + n2
     }
 }
 

 class MemoizedExample {
 
     private final Closure memoizedSum = { int n1, int n2 ->
         private$method$memoizedSum(n1,n2)
     }.memoize()
 
     int sum(int n1, int n2) {
         memoizedSum(n1, n2)
     }

     private private$method$memoizedSum(int n1, int n2) {
         println "$n1 + $n2 = ${n1 + n2}"
         n1 + n2
     }
 }
 

Upon execution of this code:

 def instance = new MemoizedExample()
 println instance.sum(1, 2)
 println instance.sum(1, 2)
 println instance.sum(2, 3)
 println instance.sum(2, 3)
 

 1 + 2 = 3
 3
 3
 2 + 3 = 5
 5
 5
 

More examples:

 import groovy.transform.*

 // Script variable which is changed when increment()
 // method is invoked. 
 // If cached method call is invoked then the value
 // of this variable will not change.
 @Field boolean incrementChange = false

 @Memoized 
 int increment(int value) {
     incrementChange = true
     value + 1 
 }

 // Invoke increment with argument 10.
 increment(10)

 // increment is invoked so incrementChange is true.
 assert incrementChange

 // Set incrementChange back to false.
 incrementChange = false

 // Invoke increment with argument 10.
 increment(10)

 // Now the cached method is used and
 // incrementChange is not changed.
 assert !incrementChange

 // Invoke increment with other argument value.
 increment(11)

 // increment is invoked so incrementChange is true.
 assert incrementChange
 

Authors:

Andrey Bloschetsov