react4j.annotations.PreUpdate Maven / Gradle / Ivy
The newest version!
package react4j.annotations;
import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Target;
/**
* Identifies a method that is called before a view is updated or re-rendered.
* There must only be one method annotated with this annotation in a view.
* This method is invoked in the "commit" phase using reacts getSnapshotBeforeUpdate()
* lifecycle method.
*
* This method is used to get access to the DOM prior to it being updated. This is useful if there is
* state stored on the DOM that is not present in the VirtualDOM. The method annotated with {@link PreUpdate}
* can query the DOM and then apply the necessary changes in {@link PostMountOrUpdate}. Scroll position is an example
* of data stored on the DOM but not present in the VirtualDOM and implementing auto-scrolling to new content
* would require use of this lifecycle method to calculate the new offset.
*
* The method must also conform to the following constraints:
*
* - Must not be annotated with any other react4j annotation
* - Must have 0 parameters
* - Must not return a value
* - Must not be private
* - Must not be public
* - Must not be static
* - Must not be abstract
* - Must not throw exceptions
* - Must be accessible from the same package as the class annotated by {@link View}
* -
* Should not be public as not expected to be invoked outside the view. A warning will be generated but can
* be suppressed by the {@link SuppressWarnings} or {@link SuppressReact4jWarnings} annotations with a key
* "React4j:PublicMethod". This warning is also suppressed by the annotation processor if it is implementing
* an interface method.
*
* -
* Should not be protected if in the class annotated with the {@link View} annotation as the method is not
* expected to be invoked outside the view. A warning will be generated but can be suppressed by the
* {@link SuppressWarnings} or {@link SuppressReact4jWarnings} annotations with a key "React4j:ProtectedMethod".
*
*
*/
@Documented
@Target( ElementType.METHOD )
public @interface PreUpdate
{
}