/*
* Copyright 2021 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 androidx.lifecycle.viewmodel
/**
* Simple map-like object that passed in [ViewModelProvider.Factory.create]
* to provide an additional information to a factory.
*
* It allows making `Factory` implementations stateless, which makes an injection of factories
* easier because don't require all information be available at construction time.
*/
public sealed class CreationExtras {
internal val map: MutableMap<Key<*>, Any?> = mutableMapOf()
/**
* Key for the elements of [CreationExtras]. [T] is a type of an element with this key.
*/
public interface Key<T>
/**
* Returns an element associated with the given [key]
*/
public abstract operator fun <T> get(key: Key<T>): T?
/**
* Empty [CreationExtras]
*/
object Empty : CreationExtras() {
override fun <T> get(key: Key<T>): T? = null
}
}
/**
* Mutable implementation of [CreationExtras]
*
* @param initialExtras extras that will be filled into the resulting MutableCreationExtras
*/
public class MutableCreationExtras(initialExtras: CreationExtras = Empty) : CreationExtras() {
init {
map.putAll(initialExtras.map)
}
/**
* Associates the given [key] with [t]
*/
public operator fun <T> set(key: Key<T>, t: T) {
map[key] = t
}
public override fun <T> get(key: Key<T>): T? {
@Suppress("UNCHECKED_CAST")
return map[key] as T?
}
}