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Create datasource for cells to make lazy-loading possible for collect…
…ions (#216) * Create datasource for cells to make lazy-loading possible for collections * Add collection test * Changelog
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,126 @@ | ||
| // | ||
| // PlanGrid | ||
| // https://www.plangrid.com | ||
| // https://medium.com/plangrid-technology | ||
| // | ||
| // Documentation | ||
| // https://plangrid.github.io/ReactiveLists | ||
| // | ||
| // GitHub | ||
| // https://github.com/plangrid/ReactiveLists | ||
| // | ||
| // License | ||
| // Copyright © 2018-present PlanGrid, Inc. | ||
| // Released under an MIT license: https://opensource.org/licenses/MIT | ||
| // | ||
|
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| import DifferenceKit | ||
| import Foundation | ||
|
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| /// Protocol for providing `CollectionViewModel`s to a `CollectionSectionViewModel` | ||
| /// | ||
| /// It is itself the `Collection` of `CollectionCellViewModel` and | ||
| /// also provides hooks for pre-fetching data | ||
| /// | ||
| /// - Note: `[TableCellViewModel]` has a default implementation | ||
| public protocol CollectionCellViewModelDataSourceProtocol: RandomAccessCollection where Element == CollectionCellViewModel, Index == Int { | ||
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| /// Called by the equivalent `UITableViewDataSourcePrefetching` method | ||
| /// - Parameter indices: The indices in the section, for which to prefetch the models | ||
| func prefetchRowsAt<S: Sequence>(indices: S) where S.Element == Int | ||
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| /// Called by the equivalent `UITableViewDataSourcePrefetching` method | ||
| /// - Parameter indices: The indices in the section, for which to cancel prefetchign the models | ||
| func cancelPrefetchingRowsAt<S: Sequence>(indices: S) where S.Element == Int | ||
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| /// The `ViewRegistrationInfo` for the cells represented by this datasource | ||
| var cellRegistrationInfo: [ViewRegistrationInfo] { get } | ||
| } | ||
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| /// The concrete data source that wraps a provided `TableCellViewModelDataSourceProtocol` implementation | ||
| public struct CollectionCellViewModelDataSource: RandomAccessCollection { | ||
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| // MARK: `CollectionCellViewModelDataSourceProtocol` wrapper blocks for type erasure | ||
|
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| /// :nodoc: | ||
| private let _subscriptBlock: (Int) -> CollectionCellViewModel | ||
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| /// :nodoc: | ||
| private let _prefetchBlock: (AnySequence<Int>) -> Void | ||
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| /// :nodoc: | ||
| private let _prefetchCancelBlock: (AnySequence<Int>) -> Void | ||
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| /// Initializes the `CollectionCellViewModelDataSource` with the provided `CollectionCellViewModelDataSourceProtocol` implementation | ||
| public init<DataSource: CollectionCellViewModelDataSourceProtocol>(_ dataSource: DataSource) { | ||
| self.init(dataSource, cellRegistrationInfo: dataSource.cellRegistrationInfo) | ||
| } | ||
|
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| /// Used internally by the public init and during diffing | ||
| /// when cached ``ViewRegistrationInfo` is available | ||
| init<DataSource: CollectionCellViewModelDataSourceProtocol>(_ dataSource: DataSource, cellRegistrationInfo: [ViewRegistrationInfo]) { | ||
| self._prefetchBlock = dataSource.prefetchRowsAt | ||
| self._prefetchCancelBlock = dataSource.cancelPrefetchingRowsAt | ||
| self._subscriptBlock = { dataSource[$0] } | ||
| self.startIndex = dataSource.startIndex | ||
| self.endIndex = dataSource.endIndex | ||
| self.cellRegistrationInfo = cellRegistrationInfo | ||
| } | ||
|
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| // MARK: - Protocol Implementation | ||
|
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| /// :nodoc: | ||
| public let cellRegistrationInfo: [ViewRegistrationInfo] | ||
|
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| /// :nodoc: | ||
| func prefetchRowsAt<S: Sequence>(indices: S) where S.Element == Int { | ||
| self._prefetchBlock(AnySequence(indices)) | ||
| } | ||
|
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| /// :nodoc: | ||
| func cancelPrefetchingRowsAt<S: Sequence>(indices: S) where S.Element == Int { self._prefetchCancelBlock(AnySequence(indices)) } | ||
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| /// :nodoc: | ||
| public typealias Element = CollectionCellViewModel | ||
|
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| /// :nodoc: | ||
| public typealias Index = Int | ||
|
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| /// :nodoc: | ||
| public subscript(position: Int) -> CollectionCellViewModel { | ||
| self._subscriptBlock(position) | ||
| } | ||
|
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| /// :nodoc: | ||
| public let startIndex: Int | ||
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| /// :nodoc: | ||
| public let endIndex: Int | ||
| } | ||
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| extension Array: CollectionCellViewModelDataSourceProtocol where Element == CollectionCellViewModel { | ||
|
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| /// :nodoc: | ||
| public func prefetchRowsAt<S: Sequence>(indices: S) where S.Element == Int {} | ||
|
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| /// :nodoc: | ||
| public func cancelPrefetchingRowsAt<S: Sequence>(indices: S) where S.Element == Int {} | ||
|
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| /// :nodoc: | ||
| public var cellRegistrationInfo: [ViewRegistrationInfo] { | ||
| self.map { | ||
| $0.registrationInfo | ||
| } | ||
| } | ||
| } | ||
|
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| //extension Array where Element == IndexPath {j | ||
| // | ||
| // /// Helper that transforms `[IndexPath]` to sequence of pairs of sections and row sequences | ||
| // func indicesBySection() -> AnySequence<(Int, AnySequence<Int>)> { | ||
| // let indexPathsBySection = [Int: [IndexPath]](grouping: self) { $0.section } | ||
| // return AnySequence(indexPathsBySection.lazy.map { section, indexPaths in | ||
| // return (section, AnySequence(indexPaths.lazy.map { $0.row })) | ||
| // }) | ||
| // } | ||
| //} |
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