| /* |
| * Copyright 2019 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.compose.runtime |
| |
| /** |
| * [key] is a utility composable that is used to "group" or "key" a block of execution inside of a |
| * composition. This is sometimes needed for correctness inside of control-flow that may cause a |
| * given composable invocation to execute more than once during composition. |
| * |
| * The value for a key *does not need to be globally unique*, and needs only be unique amongst the |
| * invocations of [key] *at that point* in composition. |
| * |
| * For instance, consider the following example: |
| * |
| * @sample androidx.compose.runtime.samples.locallyUniqueKeys |
| * |
| * Even though there are users with the same id composed in both the top and the bottom loop, |
| * because they are different calls to [key], there is no need to create compound keys. |
| * |
| * The key must be unique for each element in the collection, however, or children and local state |
| * might be reused in unintended ways. |
| * |
| * For instance, consider the following example: |
| * |
| * @sample androidx.compose.runtime.samples.notAlwaysUniqueKeys |
| * |
| * This example assumes that `parent.id` is a unique key for each item in the collection, |
| * but this is only true if it is fair to assume that a parent will only ever have a single child, |
| * which may not be the case. Instead, it may be more correct to do the following: |
| * |
| * @sample androidx.compose.runtime.samples.moreCorrectUniqueKeys |
| * |
| * A compound key can be created by passing in multiple arguments: |
| * |
| * @sample androidx.compose.runtime.samples.twoInputsKeySample |
| * |
| * @param inputs The set of values to be used to create a compound key. These will be compared to |
| * their previous values using [equals] and [hashCode] |
| * @param block The composable children for this group. |
| */ |
| @Composable |
| inline fun <T> key( |
| @Suppress("UNUSED_PARAMETER") |
| vararg inputs: Any?, |
| block: @Composable () -> T |
| ) = block() |