1 files changed, 83 insertions, 0 deletions
diff --git a/src/com/android/messaging/datamodel/binding/ImmutableBindingRef.java b/src/com/android/messaging/datamodel/binding/ImmutableBindingRef.java
new file mode 100644
index 0000000..9a0a3d6
--- /dev/null
+++ b/src/com/android/messaging/datamodel/binding/ImmutableBindingRef.java
@@ -0,0 +1,83 @@
+/*
+ * Copyright (C) 2015 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.android.messaging.datamodel.binding;
+
+import com.android.messaging.util.Assert;
+
+/**
+ * A immutable wrapper around a Binding object. Callers can only access readonly methods like
+ * getData(), isBound() and ensureBound() but not bind() and unbind(). This is used for MVC pattern
+ * where both the View and the Controller needs access to a centrally bound Model object. The View
+ * is the one that owns the bind/unbind logic of the Binding, whereas controller only serves as a
+ * consumer.
+ */
+public class ImmutableBindingRef<T extends BindableData> extends BindingBase<T> {
+    /**
+     * The referenced, read-only binding object.
+     */
+    private final BindingBase<T> mBinding;
+
+    /**
+     * Hidden ctor.
+     */
+    ImmutableBindingRef(final BindingBase<T> binding) {
+        mBinding = resolveBinding(binding);
+    }
+
+    @Override
+    public T getData() {
+        return mBinding.getData();
+    }
+
+    @Override
+    public boolean isBound() {
+        return mBinding.isBound();
+    }
+
+    @Override
+    public boolean isBound(final T data) {
+        return mBinding.isBound(data);
+    }
+
+    @Override
+    public void ensureBound() {
+        mBinding.ensureBound();
+    }
+
+    @Override
+    public void ensureBound(final T data) {
+        mBinding.ensureBound(data);
+    }
+
+    @Override
+    public String getBindingId() {
+        return mBinding.getBindingId();
+    }
+
+    /**
+     * Resolve the source binding to the real BindingImpl it's referencing. This avoids the
+     * redundancy of multiple wrapper calls when creating a binding reference from an existing
+     * binding reference.
+     */
+    private BindingBase<T> resolveBinding(final BindingBase<T> binding) {
+        BindingBase<T> resolvedBinding = binding;
+        while (resolvedBinding instanceof ImmutableBindingRef<?>) {
+            resolvedBinding = ((ImmutableBindingRef<T>) resolvedBinding).mBinding;
+        }
+        Assert.isTrue(resolvedBinding instanceof Binding<?>);
+        return resolvedBinding;
+    }
+}