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Arez Annotations

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package arez.annotations;

import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Target;
import javax.annotation.Nonnull;

/**
 * Methods marked with this annotation are memoized while there is an observer.
 *
 * The return value should be derived from the parameters and any other Observables or ComputedValues
 * within the Arez system. The value returned by the method should not change unless the parameters or the
 * state of the other {@link Observable}s change. The method is wrapped in a READ_ONLY transaction and
 * thus can not modify other state in the system.
 *
 * This is implemented by creating a separate ComputedValue instance for each unique combination of
 * parameters. When the ComputedValue is deactivated, a hook triggers that removes the ComputedValue
 * from the local cache.
 *
 * The method that is annotated with @Memoize must comply with the additional constraints:
 * 
 * Must not be annotated with any other arez annotation
 * Must have 1 or more parameters
 * Must return a value
 * Must not be private
 * Must not be static
 * Must not be final
 * Must not be abstract
 * Must not throw exceptions
 * 
 */
@Documented
@Target( ElementType.METHOD )
public @interface Memoize
{
  /**
   * Return the root name of the Memoized value relative to the component. This
   * will be used in combination with a sequence when naming the synthesized
   * ComputedValue instances. The value must conform to the requirements of a
   * java identifier. The name must also be unique across {@link Observable}s,
   * {@link Computed}s and {@link Action}s within the scope of the
   * {@link ArezComponent} annotated element.
   *
   * @return the root name of the Memoized value relative to the component.
   */
  @Nonnull
  String name() default "";
}