platform/lang-api/src/com/intellij/psi/PsiChildLink.java

   1 /*
   2  * Copyright 2000-2009 JetBrains s.r.o.
   3  *
   4  * Licensed under the Apache License, Version 2.0 (the "License");
   5  * you may not use this file except in compliance with the License.
   6  * You may obtain a copy of the License at
   7  *
   8  * http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16 package com.intellij.psi;
  17
  18 import org.jetbrains.annotations.NotNull;
  19 import org.jetbrains.annotations.Nullable;
  20
  21 /**
  22  * @author peter
  23  */
  24 public abstract class PsiChildLink<Parent extends PsiElement, Child extends PsiElement> implements PsiRefElementCreator<Parent, Child> {
  25
  26   @Nullable public abstract Child findLinkedChild(@Nullable Parent parent);
  27
  28   @NotNull
  29   public final PsiRef<Child> createChildRef(@NotNull Parent parent) {
  30     final Child existing = findLinkedChild(parent);
  31     if (existing != null) {
  32       return PsiRef.real(existing);
  33     }
  34     return PsiRef.imaginary(PsiRef.real(parent), this);
  35   }
  36
  37   @NotNull
  38   public final PsiRef<Child> createChildRef(@NotNull PsiRef<? extends Parent> parentRef) {
  39     final Parent parent = parentRef.getPsiElement();
  40     if (parent != null) {
  41       final Child existing = findLinkedChild(parent);
  42       if (existing != null) {
  43         return PsiRef.real(existing);
  44       }
  45     }
  46     return PsiRef.imaginary(parentRef, this);
  47   }
  48
  49 }