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https://github.com/cashapp/multiplatform-paging

A library that packages AndroidX Paging for Kotlin/Multiplatform.
https://github.com/cashapp/multiplatform-paging

kotlin-multiplatform

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A library that packages AndroidX Paging for Kotlin/Multiplatform.

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README 

        
# Multiplatform Paging



A library that adds additional Kotlin/Multiplatform targets to [AndroidX Paging](https://developer.android.com/topic/libraries/architecture/paging/v3-overview),

and provides UI components to use Paging on iOS.



## Introduction



As with AndroidX Paging, the primary modules of Multiplatform Paging are:



* `paging-common` – encompasses the [repository layer](https://developer.android.com/topic/libraries/architecture/paging/v3-overview#repository) and the [view model layer](https://developer.android.com/topic/libraries/architecture/paging/v3-overview#viewmodel)

* `paging-runtime` – encompasses the [UI layer](https://developer.android.com/topic/libraries/architecture/paging/v3-overview#ui)



Unlike AndroidX Paging that has a limited number of targets for `paging-common` and makes `paging-runtime` Android-specific,

Multiplatform Paging adds many more targets to `paging-common` and provides `paging-runtime-uikit`, a UIKit-specific runtime for iOS.

Therefore, pagination logic between many more targets can be shared,

and the provided UI components can be used to render the paged items on Android and iOS.



## Usage



For a holistic view of Multiplatform Paging, check out the [GitHub Repository Search sample project](samples/repo-search), where there's an Android, Desktop, and iOS app, along with shared pagination logic.



### `paging-common`



The API of `paging-common` in Multiplatform Paging is identical to that of `paging-common` in AndroidX Paging

(with the exception that: the namespace has changed from `androidx.paging` to `app.cash.paging`;

there are some minor [API discrepancies](paging-common/README.md) due to limitations in the Kotlin compiler).

Therefore, to see how to use `paging-common`, consult the [official documentation of AndroidX Paging](https://developer.android.com/topic/libraries/architecture/paging/v3-overview).



Like AndroidX Paging, all targets except for the JVM include the Paging 3 APIs only from AndroidX Paging.

There are no plans to add support for Paging 2 APIs beyond the JVM.



#### JVM, iOS, Linux X64, and macOS



`app.cash.paging:paging-common` on these targets delegate to `androidx.paging:paging-common` via type aliases.

To understand what this means in practice, see the section [_Interoperability with AndroidX Paging_](#interoperability-with-androidx-paging).



#### JS, MinGW, Linux Arm64, tvOS, and watchOS



`app.cash.paging:paging-common` on these targets delegate to _our fork_ of AndroidX Paging.



### `paging-compose-common`



The API of `paging-compose-common` in Multiplatform Paging is identical to that of `paging-compose` in AndroidX Paging

(with the exception that the namespace has changed from `androidx.paging` to `app.cash.paging`).



To see how to use `paging-compose-common`, consult the [official documentation of AndroidX Paging](https://developer.android.com/reference/kotlin/androidx/paging/compose/package-summary#(kotlinx.coroutines.flow.Flow).collectAsLazyPagingItems(kotlin.coroutines.CoroutineContext)).



#### Android



`app.cash.paging:paging-compose-common` on Android delegates to `androidx.paging:paging-compose` via type aliases.

To understand what this means in practice, see the section [_Interoperability with AndroidX Paging_](#interoperability-with-androidx-paging).



#### JVM, iOS, JS, JVM, Linux X64, macOS, MinGW, tvOS, and watchOS



`app.cash.paging:paging-compose-common` on the these targets delegate to _our fork_ of AndroidX Paging.



### `paging-runtime` for Android



See the [_Interoperability with AndroidX Paging_](#interoperability-with-androidx-paging) section below.



### `paging-runtime-uikit` for iOS



The `PagingCollectionViewController` allows a `PagingData` to be rendered via a `UICollectionView`.

The `PagingCollectionViewController` mimics the `UICollectionViewController`,

providing: the cell count; and item retrieval via `IndexPath`.



Here's an example in Swift:



```swift

final class FooViewController: UICollectionViewController {



  private let delegate = Paging_runtime_uikitPagingCollectionViewController()



  private let presenter = …



  required init(coder: NSCoder) {

    super.init(coder: coder)!

    presenter.pagingDatas

      .sink { pagingData in

        self.delegate.submitData(pagingData: pagingData, completionHandler: …)

      }

  }



  override func collectionView(

    _ collectionView: UICollectionView,

    numberOfItemsInSection section: Int

  ) -> Int {

    return Int(delegate.collectionView(collectionView: collectionView, numberOfItemsInSection: Int64(section)))

  }



  override func collectionView(

    _ collectionView: UICollectionView,

    cellForItemAt indexPath: IndexPath

  ) -> UICollectionViewCell {

    let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "FooCell", for: indexPath) as! FooCell



    let item = delegate.getItem(position: Int32(indexPath.row))!

    // …



    return cell

  }

}

```



### `paging-testing`



The API of `paging-testing` in Multiplatform Paging is identical to that of `paging-testing` in AndroidX Paging

(with the exception that the namespace has changed from `androidx.paging` to `app.cash.paging`).

Therefore, to see how to use `paging-testing`, consult the [official documentation of AndroidX Paging](https://developer.android.com/topic/libraries/architecture/paging/test).



#### JVM, iOS, Linux X64, and macOS



`app.cash.paging:paging-testing` on these targets delegate to `androidx.paging:paging-testing` via type aliases.

To understand what this means in practice, see the section [_Interoperability with AndroidX Paging_](#interoperability-with-androidx-paging).



#### JS, MinGW, Linux Arm64, tvOS, and watchOS



`app.cash.paging:paging-common` on these targets delegate to _our fork_ of AndroidX Paging.



## Interoperability with AndroidX Paging



As `app.cash.paging:paging-common` on the JVM, iOS, Linux X64, and macOS type alias to `androidx.paging:paging-common`,

some useful side effects occur:



* The implementation of `app.cash.paging:paging-common` on the JVM, iOS, Linux X64, and macOS is **identical** to `androidx.paging:paging-common`.

  This means that it is impossible for there to be a behavioral discrepancy when using `app.cash.paging:paging-common` on the JVM, iOS, Linux X64, or macOS.

* All libraries that depend on `androidx.paging:paging-common` can continue to be used. 

  Some JVM-specific examples include `androidx.paging:paging-runtime`, `androidx.paging:paging-compose`, and `androidx.paging:paging-rxjava3`.

  This is why there aren't additional `paging-runtime` artifacts to support Android's UI toolkit,

  as you can instead depend on the official AndroidX artifact.

* If you're already using AndroidX Paging, you don't need to refactor your existing codebase to begin using Multiplatform Paging.

  The use of Multiplatform Paging is only necessary if you wish to share pagination logic on targets that AndroidX Paging don't yet support, or you want to use pagination UI bindings on platforms like iOS via `paging-runtime-uikit`. 



A similar argument can be made for `app.cash.paging:paging-compose-common` and `app.cash.paging:paging-testing`.



## Releases



The versioning scheme is of the form `X-Y` where:



- `X` is the AndroidX Paging version that is being tracked.

- `Y` is the Multiplatform Paging version.



For example, if AndroidX Paging is on `3.3.0-alpha02` and Multiplatform Paging is on `0.4.0`,

the artifact for a release of `paging-common` will be `app.cash.paging:paging-common:3.3.0-alpha02-0.4.0`.



### `paging-common` for common



```kotlin

implementation("app.cash.paging:paging-common:3.3.0-alpha02-0.4.0")

```



### `paging-compose-common` for common



```kotlin

implementation("app.cash.paging:paging-compose-common:3.3.0-alpha02-0.4.0")

```



### `paging-runtime-uikit` for iOS



```kotlin

implementation("app.cash.paging:paging-runtime-uikit:3.3.0-alpha02-0.4.0")

```



### `paging-testing` for common



```kotlin

implementation("app.cash.paging:paging-testing:3.3.0-alpha02-0.4.0")

```



### Android



Use the [official AndroidX Paging dependencies](https://developer.android.com/jetpack/androidx/releases/paging#declaring_dependencies).



```kotlin

implementation("androidx.paging:paging-runtime:3.3.0-alpha02")

implementation("androidx.paging:paging-compose:3.3.0-alpha02")

implementation("androidx.paging:paging-rxjava3:3.3.0-alpha02")

// etc.

```



## License



    Copyright 2022 Block, Inc.



    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.