1/*
2 * Copyright (C) 2015 The Android Open Source Project
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 */
16package com.android.messaging.datamodel.binding;
17
18/**
19 * The binding class keeps track of a binding between a ui component and an item of BindableData
20 * It allows each side to ensure that when it communicates with the other they are still bound
21 * together.
22 * NOTE: Ensure that the UI component uses the same binding instance for it's whole lifetime
23 *  (DO NOT CREATE A NEW BINDING EACH TIME A NEW PIECE OF DATA IS BOUND)...
24 *
25 * The ui component owns the binding instance.
26 * It can use it [isBound(data)] to see if the binding still binds to the right piece of data
27 *
28 * Upon binding the data is informed of a unique binding key generated in this class and can use
29 * that to ensure that it is still issuing callbacks to the right piece of ui.
30 */
31public abstract class BindingBase<T extends BindableData> {
32    /**
33     * Creates a new exclusively owned binding for the owner object.
34     */
35    public static <T extends BindableData> Binding<T> createBinding(final Object owner) {
36        return new Binding<T>(owner);
37    }
38
39    /**
40     * Creates a new read-only binding referencing the source binding object.
41     * TODO: We may want to refcount the Binding references, so that when the binding owner
42     * calls unbind() when there's still outstanding references we can catch it.
43     */
44    public static <T extends BindableData> ImmutableBindingRef<T> createBindingReference(
45            final BindingBase<T> srcBinding) {
46        return new ImmutableBindingRef<T>(srcBinding);
47    }
48
49    /**
50     * Creates a detachable binding for the owner object. Use this if your owner object is a UI
51     * component that may undergo a "detached from window" -> "re-attached to window" transition.
52     */
53    public static <T extends BindableData> DetachableBinding<T> createDetachableBinding(
54            final Object owner) {
55        return new DetachableBinding<T>(owner);
56    }
57
58    public abstract T getData();
59
60    /**
61     * Check if binding connects to the specified data instance
62     */
63    public abstract boolean isBound();
64
65    /**
66     * Check if binding connects to the specified data instance
67     */
68    public abstract boolean isBound(final T data);
69
70    /**
71     * Throw if binding connects to the specified data instance
72     */
73    public abstract void ensureBound();
74
75    /**
76     * Throw if binding connects to the specified data instance
77     */
78    public abstract void ensureBound(final T data);
79
80    /**
81     * Return the binding id for this binding (will be null if not bound)
82     */
83    public abstract String getBindingId();
84}
85