RxSwift官方实例七（UIPickerView）

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UIPickerView的Rx实现分析

RxPickerViewDelegateProxy分析

RxCocoa

已经实现了

RxPickerViewDelegateProxy

，该类继承

DelegateProxy

基类，遵守

DelegateProxyType

、

UIPickerViewDelegate

协议：

extension UIPickerView: HasDelegate {
        public typealias Delegate = UIPickerViewDelegate
    }

    open class RxPickerViewDelegateProxy
        : DelegateProxy<UIPickerView, UIPickerViewDelegate>
        , DelegateProxyType 
        , UIPickerViewDelegate {

        /// Typed parent object.
        public weak private(set) var pickerView: UIPickerView?

        /// - parameter pickerView: Parent object for delegate proxy.
        public init(pickerView: ParentObject) {
            self.pickerView = pickerView
            super.init(parentObject: pickerView, delegateProxy: RxPickerViewDelegateProxy.self)
        }

        // Register known implementationss
        public static func registerKnownImplementations() {
            self.register { RxPickerViewDelegateProxy(pickerView: $0) }
        }
    }

UIPickerViewDelegate

协议的所有函数在这个类中都没有实现，最终会进行消息转发。

RxPickerViewDataSourceProxy分析

RxCocoa

已经实现了

RxPickerViewDataSourceProxy

，该类继承

DelegateProxy

基类，遵守

DelegateProxyType

、

UIPickerViewDataSource

协议：

extension UIPickerView: HasDataSource {
    public typealias DataSource = UIPickerViewDataSource
}

private let pickerViewDataSourceNotSet = PickerViewDataSourceNotSet()

final private class PickerViewDataSourceNotSet: NSObject, UIPickerViewDataSource {
    func numberOfComponents(in pickerView: UIPickerView) -> Int {
        return 0
    }
    
    func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
        return 0
    }
}

/// For more information take a look at `DelegateProxyType`.
public class RxPickerViewDataSourceProxy
    : DelegateProxy<UIPickerView, UIPickerViewDataSource>
    , DelegateProxyType
    , UIPickerViewDataSource {

    /// Typed parent object.
    public weak private(set) var pickerView: UIPickerView?

    /// - parameter pickerView: Parent object for delegate proxy.
    public init(pickerView: ParentObject) {
        self.pickerView = pickerView
        super.init(parentObject: pickerView, delegateProxy: RxPickerViewDataSourceProxy.self)
    }

    // Register known implementations
    public static func registerKnownImplementations() {
        self.register { RxPickerViewDataSourceProxy(pickerView: $0) }
    }

    private weak var _requiredMethodsDataSource: UIPickerViewDataSource? = pickerViewDataSourceNotSet

    // MARK: UIPickerViewDataSource

    /// Required delegate method implementation.
    public func numberOfComponents(in pickerView: UIPickerView) -> Int {
        return (_requiredMethodsDataSource ?? pickerViewDataSourceNotSet).numberOfComponents(in: pickerView)
    }

    /// Required delegate method implementation.
    public func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
        return (_requiredMethodsDataSource ?? pickerViewDataSourceNotSet).pickerView(pickerView, numberOfRowsInComponent: component)
    }
    
    /// For more information take a look at `DelegateProxyType`.
    public override func setForwardToDelegate(_ forwardToDelegate: UIPickerViewDataSource?, retainDelegate: Bool) {
        _requiredMethodsDataSource = forwardToDelegate ?? pickerViewDataSourceNotSet
        super.setForwardToDelegate(forwardToDelegate, retainDelegate: retainDelegate)
    }
}

扩展UIPickerView遵守HasDataSource协议，使

RxPickerViewDataSourceProxy

满足条件进而实现了

DelegateProxyType

协议中定义的如下两个函数：

extension DelegateProxyType where ParentObject: HasDataSource, Self.Delegate == ParentObject.DataSource {
    public static func currentDelegate(for object: ParentObject) -> Delegate? {
        return object.dataSource
    }

    public static func setCurrentDelegate(_ delegate: Delegate?, to object: ParentObject) {
        object.dataSource = delegate
    }
}

定义

PickerViewDataSourceNotSet

这个类为

UIPickerViewDataSource

协议提供默认数据

重写

setForwardToDelegate

函数，将参数

forwardToDelegate

存储在私有属性

_requiredMethodsDataSource

中。

UIPickerViewDataSource

协议中的两个函数在这个类中实现，调用属性

_requiredMethodsDataSource

的方法返回结果。

RxPickerViewAdapter分析

RxPickerViewAdapter

是用来处理

UIPickerViewDataSource

、

UIPickerViewDelegate

协议中定义的带有返回值的函数的。

RxCocoa

实现了3种

RxPickerViewAdapter

，分别是

RxStringPickerViewAdapter

、

RxAttributedStringPickerViewAdapter

、

RxPickerViewAdapter

。

RxPickerViewArrayDataSource分析

RxPickerViewArrayDataSource

是

RxStringPickerViewAdapter

、

RxAttributedStringPickerViewAdapter

、

RxPickerViewAdapter

的根类，遵守

UIPickerViewDataSource

、

SectionedViewDataSourceType

协议，还定义一个泛型

<T>

作为通用数据类型：

class RxPickerViewArrayDataSource<T>: NSObject, UIPickerViewDataSource, SectionedViewDataSourceType {
    fileprivate var items: [T] = []
    
    func model(at indexPath: IndexPath) throws -> Any {
        guard items.indices ~= indexPath.row else {
            throw RxCocoaError.itemsNotYetBound(object: self)
        }
        return items[indexPath.row]
    }

    func numberOfComponents(in pickerView: UIPickerView) -> Int {
        return 1
    }
    
    func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
        return items.count
    }
}

items 数组属性存储所需数据，问题是他只能存一组数据。
实现 UIPickerViewDataSource 协议。

RxPickerViewSequenceDataSource分析

RxPickerViewSequenceDataSource

这个类继承自

RxPickerViewArrayDataSource

，是

RxStringPickerViewAdapter

、

RxAttributedStringPickerViewAdapter

、

RxPickerViewAdapter

的父类，遵守

RxPickerViewArrayDataSource<Sequence.Element>

RxPickerViewDataSourceType

协议，定义一个遵守

Swift.Sequence

协议的泛型

<Sequence>

：

class RxPickerViewSequenceDataSource<Sequence: Swift.Sequence>
    : RxPickerViewArrayDataSource<Sequence.Element>
    , RxPickerViewDataSourceType {
    typealias Element = Sequence

    func pickerView(_ pickerView: UIPickerView, observedEvent: Event<Sequence>) {
        Binder(self) { dataSource, items in
            dataSource.items = items
            pickerView.reloadAllComponents()
        }
        .on(observedEvent.map(Array.init))
    }
}

func pickerView(_ pickerView: UIPickerView, observedEvent: Event<Sequence>)

函数的实现：

构建一个 Binder 并执行 on 操作，实际相当于直接执行构建 Binder 的 binding 闭包。
将 Event<Sequence> 类型参数 observedEvent 转化为 Event<Array> 作为 on 操作的参数。
在构建 Binder 的 binding 闭包中，将数组赋值给 items 属性并刷新整个 UIPickerView 。

RxStringPickerViewAdapter、RxAttributedStringPickerViewAdapter、RxPickerViewAdapter分析

RxStringPickerViewAdapter

是不可被继承的，自身继承自

RxPickerViewSequenceDataSource

并且遵守

UIPickerViewDelegate

协议：

final class RxStringPickerViewAdapter<Sequence: Swift.Sequence>
    : RxPickerViewSequenceDataSource<Sequence>
    , UIPickerViewDelegate {
    
    typealias TitleForRow = (Int, Sequence.Element) -> String?
    private let titleForRow: TitleForRow
    
    init(titleForRow: @escaping TitleForRow) {
        self.titleForRow = titleForRow
        super.init()
    }
    
    func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {
        return titleForRow(row, items[row])
    }
}

属性

titleForRow

存储将

items

数组中的元素转化为

String

类型的闭包。

- (nullable NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component

函数中执行

titleForRow

闭包并返回其结果。

RxAttributedStringPickerViewAdapter

、

RxPickerViewAdapter

的实现与

RxStringPickerViewAdapter

类似，不同的是分别存储

attributedTitleForRow

（将数组中元素转化为

NSAttributedString

富文本）、

viewForRow

（将数组中元素转化为

UIView

视图）的闭包，实现不同的

UIPickerViewDelegate

协议函数返回执行闭包的返回值：

final class RxAttributedStringPickerViewAdapter<Sequence: Swift.Sequence>: RxPickerViewSequenceDataSource<Sequence>, UIPickerViewDelegate {
    typealias AttributedTitleForRow = (Int, Sequence.Element) -> NSAttributedString?
    private let attributedTitleForRow: AttributedTitleForRow
    
    init(attributedTitleForRow: @escaping AttributedTitleForRow) {
        self.attributedTitleForRow = attributedTitleForRow
        super.init()
    }
    
    func pickerView(_ pickerView: UIPickerView, attributedTitleForRow row: Int, forComponent component: Int) -> NSAttributedString? {
        return attributedTitleForRow(row, items[row])
    }
}

final class RxPickerViewAdapter<Sequence: Swift.Sequence>: RxPickerViewSequenceDataSource<Sequence>, UIPickerViewDelegate {
    typealias ViewForRow = (Int, Sequence.Element, UIView?) -> UIView
    private let viewForRow: ViewForRow
    
    init(viewForRow: @escaping ViewForRow) {
        self.viewForRow = viewForRow
        super.init()
    }
    
    func pickerView(_ pickerView: UIPickerView, viewForRow row: Int, forComponent component: Int, reusing view: UIView?) -> UIView {
        return viewForRow(row, items[row], view)
    }
}

基于UIPickerView的Reactive扩展分析

定义delegate、dataSource两个函数用于获取Rx代理对象，方便使用：

public var delegate: DelegateProxy<UIPickerView, UIPickerViewDelegate> {
            return RxPickerViewDelegateProxy.proxy(for: base)
        }
        public var dataSource: DelegateProxy<UIPickerView, UIPickerViewDataSource> {
            return RxPickerViewDataSourceProxy.proxy(for: base)
        }

定义setDelegate函数通过

installForwardDelegate

函数为Rx代理对象设置

forwardDelegate

并返回一个置空

forwardDelegate

的

Disposables

：

public func setDelegate(_ delegate: UIPickerViewDelegate)
            -> Disposable {
                return RxPickerViewDelegateProxy.installForwardDelegate(delegate, retainDelegate: false, onProxyForObject: self.base)
        }

public func items<Source: ObservableType, Adapter: RxPickerViewDataSourceType & UIPickerViewDataSource & UIPickerViewDelegate>(adapter: Adapter) -> (_ source: Source) -> Disposable where Source.Element == Adapter.Element

函数，这个函数很重要，数据的绑定最终都会走到这个函数：

public func items<Source: ObservableType,
                          Adapter: RxPickerViewDataSourceType & UIPickerViewDataSource & UIPickerViewDelegate>(adapter: Adapter)
            -> (_ source: Source)
            -> Disposable where Source.Element == Adapter.Element {
                return { source in
                    let delegateSubscription = self.setDelegate(adapter)
                    let dataSourceSubscription = source.subscribeProxyDataSource(ofObject: self.base, dataSource: adapter, retainDataSource: true, binding: { [weak pickerView = self.base] (_: RxPickerViewDataSourceProxy, event) in
                        guard let pickerView = pickerView else { return }
                        adapter.pickerView(pickerView, observedEvent: event)
                    })
                    return Disposables.create(delegateSubscription, dataSourceSubscription)
                }
        }

此函数接收一个遵守 RxPickerViewDataSourceType 、 UIPickerViewDataSource 、 UIPickerViewDelegate 这三个协议的参数 adapter ，返回一个 (_ source: Source) -> Disposable 绑定数据的闭包
构建返回闭包，将原函数参数 adapter 通过 setDelegate 函数设置给 RxDelegate 代理对象的 forwardDelegate 。
将原函数参数 adapter 通过原函数参数 source 的 subscribeProxyDataSource （见下方分析）函数设置给 RxDataSource 代理对象的 forwardDelegate ，并在 binding 参数的闭包中执行 adapter 的 func pickerView(_ pickerView: UIPickerView, observedEvent: Event<Element>) 函数绑定数据。
最后将 setDelegate 和 subscribeProxyDataSource 函数返回的 Disposables 组合成一个 Disposables 返回。

itemTitles

，

itemAttributedTitles

，

items

这三个函数分别是将一个

Observable

中的数据绑定到

UIPickerView

的标题、富文本标题、以及view上：

public func itemTitles<Sequence: Swift.Sequence, Source: ObservableType>
            (_ source: Source)
            -> (_ titleForRow: @escaping (Int, Sequence.Element) -> String?)
            -> Disposable where Source.Element == Sequence {
                return { titleForRow in
                    let adapter = RxStringPickerViewAdapter<Sequence>(titleForRow: titleForRow)
                    return self.items(adapter: adapter)(source)
                }
        }
        public func itemAttributedTitles<Sequence: Swift.Sequence, Source: ObservableType>
            (_ source: Source)
            -> (_ attributedTitleForRow: @escaping (Int, Sequence.Element) -> NSAttributedString?)
            -> Disposable where Source.Element == Sequence {
                return { attributedTitleForRow in
                    let adapter = RxAttributedStringPickerViewAdapter<Sequence>(attributedTitleForRow: attributedTitleForRow)
                    return self.items(adapter: adapter)(source)
                }
        }
        public func items<Sequence: Swift.Sequence, Source: ObservableType>
            (_ source: Source)
            -> (_ viewForRow: @escaping (Int, Sequence.Element, UIView?) -> UIView)
            -> Disposable where Source.Element == Sequence {
                return { viewForRow in
                    let adapter = RxPickerViewAdapter<Sequence>(viewForRow: viewForRow)
                    return self.items(adapter: adapter)(source)
                }
        }

这三个函数的形式都是一样的，接收一个 Observable 序列的数据参数，返回一个闭包。
不同的是返回的闭包的参数不一样，分别是将原函数 Observable 序列的元素转化为 String 、 NSAttributedString 、 UIView 的闭包。
原函数都是直接构建一个闭包返回，在闭包中将转换原函数 Observable 序列的元素的闭包参数分别构建为 RxStringPickerViewAdapter 、 RxAttributedStringPickerViewAdapter 、 RxPickerViewAdapter 对象，然后调用前面分析的 public func items<Source: ObservableType, Adapter: RxPickerViewDataSourceType & UIPickerViewDataSource & UIPickerViewDelegate>(adapter: Adapter) -> (_ source: Source) -> Disposable where Source.Element == Adapter.Element 函数通过各自的 adapter 将将原函数 Observable 序列的元素绑定到 UIPickerView 并返回 Disposable 。

public func model<T>(at indexPath: IndexPath) throws -> T

函数用于获取每个单元格中的数据对象：

public func model<T>(at indexPath: IndexPath) throws -> T {
            let dataSource: SectionedViewDataSourceType = castOrFatalError(self.dataSource.forwardToDelegate(), message: "This method only works in case one of the `rx.itemTitles, rx.itemAttributedTitles, items(_ source: O)` methods was used.")
            
            return castOrFatalError(try dataSource.model(at: indexPath))
        }

取出 self.dataSource.forwardToDelegate() 对象，实际上就是前面设置的 adapter 对象。
由于 adapter 对象的基类 RxPickerViewArrayDataSource 实现了 SectionedViewDataSourceType 协议中定义的 func model(at indexPath: IndexPath) throws -> Any 函数，所以返回其调用结果。

使用消息转发的方式实现

itemSelected

序列，并使用

map

操作符更改序列元素。

modelSelected

序列是通过

itemSelected

序列进行转化而来：

public var itemSelected: ControlEvent<(row: Int, component: Int)> {
            let source = delegate
                .methodInvoked(#selector(UIPickerViewDelegate.pickerView(_:didSelectRow:inComponent:)))
                .map {
                    return (row: try castOrThrow(Int.self, $0[1]), component: try castOrThrow(Int.self, $0[2]))
                }
            return ControlEvent(events: source)
        }
        public func modelSelected<T>(_ modelType: T.Type) -> ControlEvent<[T]> {
            let source = itemSelected.flatMap { [weak view = self.base as UIPickerView] _, component -> Observable<[T]> in
                guard let view = view else {
                    return Observable.empty()
                }

                let model: [T] = try (0 ..< view.numberOfComponents).map { component in
                    let row = view.selectedRow(inComponent: component)
                    return try view.rx.model(at: IndexPath(row: row, section: component))
                }

                return Observable.just(model)
            }
            
            return ControlEvent(events: source)
        }

ObservableType扩展分析

func subscribeProxyDataSource<DelegateProxy: DelegateProxyType>(ofObject object: DelegateProxy.ParentObject, dataSource: DelegateProxy.Delegate, retainDataSource: Bool, binding: @escaping (DelegateProxy, Event<Element>) -> Void) -> Disposable

函数的作用是为

Rx

代理对象设置

forwardDelegate

对象和订阅自身时执行

binding

参数中的闭包相关操作：

extension ObservableType {
            func subscribeProxyDataSource<DelegateProxy: DelegateProxyType>(ofObject object: DelegateProxy.ParentObject, dataSource: DelegateProxy.Delegate, retainDataSource: Bool, binding: @escaping (DelegateProxy, Event<Element>) -> Void)
                -> Disposable
                where DelegateProxy.ParentObject: UIView
                , DelegateProxy.Delegate: AnyObject {
                let proxy = DelegateProxy.proxy(for: object)
                let unregisterDelegate = DelegateProxy.installForwardDelegate(dataSource, retainDelegate: retainDataSource, onProxyForObject: object)
                // this is needed to flush any delayed old state (https://github.com/RxSwiftCommunity/RxDataSources/pull/75)
                object.layoutIfNeeded()

                let subscription = self.asObservable()
                    .observeOn(MainScheduler())
                    .catchError { error in
                        bindingError(error)
                        return Observable.empty()
                    }
                    // source can never end, otherwise it would release the subscriber, and deallocate the data source
                    .concat(Observable.never())
                    .takeUntil(object.rx.deallocated)
                    .subscribe { [weak object] (event: Event<Element>) in

                        if let object = object {
                            assert(proxy === DelegateProxy.currentDelegate(for: object), "Proxy changed from the time it was first set.\nOriginal: \(proxy)\nExisting: \(String(describing: DelegateProxy.currentDelegate(for: object)))")
                        }
                        
                        binding(proxy, event)
                        
                        switch event {
                        case .error(let error):
                            bindingError(error)
                            unregisterDelegate.dispose()
                        case .completed:
                            unregisterDelegate.dispose()
                        default:
                            break
                        }
                    }
                    
                return Disposables.create { [weak object] in
                    subscription.dispose()
                    object?.layoutIfNeeded()
                    unregisterDelegate.dispose()
                }
            }
        }

这个函数接收三个参数分别是Rx代理对象的持有者 object 、Rx代理类关联类型 Delegate 的 dataSource 、是否持有 dataSource 的 retainDataSource 、数据绑定闭包 binding 。
首先调用Rx代理类的 proxy 函数获得Rx代理对象，接着调用 installForwardDelegate 函数设置Rx代理对象的 forwardDelegate 。
然后本 Observable 序列执行 subscribe 操作进行订阅并在其参数 on 闭包中执行 binding 闭包。
最后将自身订阅和 installForwardDelegate 函数放回的 Disposable 组合成一个返回。

UIPickerView示例

简单的绑定

构建3个UIPickerView分别为pickerView1、pickerView2、pickerView3……

然后构建数据并分别绑定到上面的3个UIPickerView：

// 绑定pickerView1
        Observable.just([1, 2, 3, 4, 5, 6, 7, 8, 9])
            .bind(to: pickerView1.rx.itemTitles, curriedArgument: { "\($1)" })
            .disposed(by: bag)
        pickerView1.rx.itemSelected
            .subscribe(onNext: { print("选中了第\($1)列第\($0)行") })
            .disposed(by: bag)
        pickerView1.rx.modelSelected(Int.self)
            .subscribe(onNext: { print("选中了元素\($0.first ?? 0)") })
            .disposed(by: bag)
        
        // 绑定pickerView2
        Observable.just([1, 2, 3, 4, 5, 6, 7, 8, 9])
            .bind(to: pickerView2.rx.itemAttributedTitles, curriedArgument: { NSAttributedString(string: "\($1)", attributes: [NSAttributedString.Key.foregroundColor: UIColor.random]) })
            .disposed(by: bag)
        
        pickerView2.rx.itemSelected
            .subscribe(onNext: { print("选中了第\($1)列第\($0)行") })
            .disposed(by: bag)
        
        pickerView2.rx.modelSelected(Int.self)
            .subscribe(onNext: { print("选中了元素\($0.first ?? 0)") })
            .disposed(by: bag)
        
        // 绑定pickerView3
        Observable.just(Array(0..<10).map({ (_) -> UIColor in UIColor.random }))
            .bind(to: pickerView3.rx.items, curriedArgument: { _, color, _ in
                let view = UIView()
                view.backgroundColor = color
                return view
            }).disposed(by: bag)
        pickerView3.rx.itemSelected
            .subscribe(onNext: { print("选中了第\($1)列第\($0)行") })
            .disposed(by: bag)
        pickerView3.rx.modelSelected(UIColor.self)
            .subscribe(onNext: { print("选中了元素\($0.first ?? UIColor.white)") })
            .disposed(by: bag)

数据绑定过程分析

Observable.just([1, 2, 3, 4, 5, 6, 7, 8, 9])
            .bind(to: pickerView1.rx.itemTitles, curriedArgument: { "\($1)" })
            .disposed(by: bag)

RxCocoa对

func bind<R1, R2>(to binder: (Self) -> (R1) -> R2, curriedArgument: R1) -> R2

函数的实现：

public func bind<R1, R2>(to binder: (Self) -> (R1) -> R2, curriedArgument: R1) -> R2 {
         return binder(self)(curriedArgument)
    }

泛型

R1

为

(Int, Sequence.Element) -> String?

类型闭包，泛型

R2

为

Disposable

类型。于是上面数据绑定的代码等价于：

pickerView1.rx
            .itemTitles(Observable.just([1, 2, 3, 4, 5, 6, 7, 8, 9]))({ "\($1)" })
            .disposed(by: bag)

数据绑定的完整过程：

构建元素是一个 [int] 类型的原数据 Observable 序列。
把原数据 Observable 序列作为参数执行 pickerView1.rx.itemTitles 函数，返回一个 (titleForRow: (Int, Sequence.Element) -> String?) -> Disposable 类型的闭包。
将类型为 (Int, Sequence.Element) -> String? 的参数 curriedArgument 这个闭包再作为 titleForRow 参数执行上面的 (titleForRow: (Int, Sequence.Element) -> String?) -> Disposable 闭包。
(titleForRow: (Int, Sequence.Element) -> String?) -> Disposable 闭包内部使用 titleForRow 闭包构建 RxStringPickerViewAdapter 类型对象 adapter 。
然后用 adapter 作为参数执行 func items(adapter: Adapter) -> (source: Source) -> Disposable 函数返回类型为 (source: Source) -> Disposable 的闭包。
将原数据 Observable 序列作为参数执行 (source: Source) -> Disposable 闭包。
闭包 (source: Source) -> Disposable 内部执行 setDelegate 函数设置 RxPickerViewDelegateProxy 类型的 forwardDelegate 属性。
闭包 (source: Source) -> Disposable 内部执行 subscribeProxyDataSource 函数设置 RxPickerViewDataSourceProxy 类型的 forwardDelegate 属性。
subscribeProxyDataSource 函数内部订阅原数据 Observable 序列将 [int] 类型的元素作为参数执行 adapter 对象的 func pickerView(pickerView: UIPickerView, observedEvent: Event<Element>) 函数。
最后 func pickerView(pickerView: UIPickerView, observedEvent: Event<Element>) 函数中将 [int] 类型的元素保存到 adapter 对象的 items 属性中并执行 reloadAllComponents 刷新 UIPickerView 。
UIPickerView 在刷新时会调用其代理对象（ RxPickerViewDelegateProxy 、 RxPickerViewDataSourceProxy ）的函数，然后在实现的协议函数中执行其 forwardDelegate 属性相应的函数返回数据或者通过消息转发的方式执行 forwardDelegate 中的函数。

pickerView1.rx.itemSelected
            .subscribe(onNext: { print("选中了第\($1)列第\($0)行") })
            .disposed(by: bag)
        pickerView1.rx.modelSelected(Int.self)
            .subscribe(onNext: { print("选中了元素\($0.first ?? 0)") })
            .disposed(by: bag)

itemSelected 通过消息转发实现。
modelSelected 将 itemSelected 通过 flatMap 操作符转化 Observable 序列的行列号元素为实际数据。

pickerView1

、

pickerView2

、

pickerView3

的数据绑定过程是一样的。区别无非是将数据分别绑定到单元格的

title

、

attributedTitle

、

view

。

自定义绑定

从对

RxPickerViewArrayDataSource

的分析可以看出

RxCocoa

只实现了将单组数据绑定到

UIPickerView

单元格的

title

、

attributedTitle

、

view

。

这往往满足不了日常的开发需要，所以自定义绑定显得很重要。

实现多组数据绑定

参照

RxCocoa

实现的

RxStringPickerViewAdapter

、

RxAttributedStringPickerViewAdapter

、

RxPickerViewAdapter

实现一个支持多组数据的基类

BaseSectionedPickerViewAdapter

：

class BaseSectionedPickerViewAdapter: NSObject, UIPickerViewDataSource, UIPickerViewDelegate, RxPickerViewDataSourceType, SectionedViewDataSourceType {
    typealias Element = [[CustomStringConvertible]]
    fileprivate var items: Element = []
    
    func model(at indexPath: IndexPath) throws -> Any {
        items[indexPath.section][indexPath.row]
    }
    
    func numberOfComponents(in pickerView: UIPickerView) -> Int {
        items.count
    }
    func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
        items[component].count
    }
    
    func pickerView(_ pickerView: UIPickerView, observedEvent: Event<[[CustomStringConvertible]]>) {
        Binder(self) { (adapter, items) in
            adapter.items = items
            pickerView.reloadAllComponents()
        }.on(observedEvent)
    }
}

实现一个简单的

SimpleSectionedPickerViewAdapter

，实现

func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String?

函数将数据的

description

属性简单地绑定到

title

上：

class SimpleSectionedPickerViewAdapter: BaseSectionedPickerViewAdapter {
    func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {
        return items[component][row].description
    }
}

在页面上搭建一个

UIPickerView

命名为

pickerView

，然后进行数据绑定：

Observable.just([Array(0..<10), Array(10..<20), Array(20..<30)])
            .bind(to: pickerView.rx.items(adapter: SimpleSectionedPickerViewAdapter()))
            .disposed(by: bag)

RxCocoa

对

func bind<Result>(to binder: (Self) -> Result) -> Result

函数的实现：

public func bind<Result>(to binder: (Self) -> Result) -> Result {
        return binder(self)
    }

泛型

Result

为

Disposable

类型。于是上面数据绑定的代码等价于：

pickerView.rx
            .items(adapter: SimpleSectionedPickerViewAdapter())(Observable.just([Array(0..<10), Array(10..<20), Array(20..<30)]))
            .disposed(by: bag)

数据绑定的完整过程：

首先构建一个 Observable 序列的原数据 Observable.just([Array(0..<10), Array(10..<20), Array(20..<30)])
构建一个 PickerViewViewAdapter 类型对象作为参数执行 func items(adapter: Adapter) -> (_ source: Source) -> Disposable 函数返回类型为 (source: Source) -> Disposable 的闭包。
将原数据 Observable 序列作为参数执行 (source: Source) -> Disposable 闭包。
接下来的过程与上面的简单绑定过程完全一致。

就这样实现了多组数据的简单绑定，但是实际开发中往往需要控制

UIPickerView

单元格的宽、高、标题、视图等内容，接下来实现更全面的数据绑定。

实现完整的数据绑定

实现一个

SectionedPickerViewAdapter

，与Rxcocoa实现的

RxPickerViewAdapter

类似：

class 
<T: CustomStringConvertible>: BaseSectionedPickerViewAdapter<T>, UIPickerViewDelegate {
    private var viewForRow: ((UIPickerView, Int, Int, UIView?) -> UIView)?
    private var titleForRow: ((UIPickerView, Int, Int) -> String)?
    private var attributedTitleForRow: ((UIPickerView, Int, Int) -> NSAttributedString)?
    private var widthForComponent: ((UIPickerView, Int) -> CGFloat)?
    private var heightForComponent: ((UIPickerView, Int) -> CGFloat)?
    
    func pickerView(_ pickerView: UIPickerView, viewForRow row: Int, forComponent component: Int, reusing view: UIView?) -> UIView {
        if let aView = viewForRow {
            return aView(pickerView, row, component, view)
        } else {
            let label = UILabel()
            label.textAlignment = .center
            label.font = UIFont.systemFont(ofSize: 21.0)
            if let aAttributedTitle = attributedTitleForRow {
                label.attributedText = aAttributedTitle(pickerView, row, component)
            }
            else if let aTitle = titleForRow {
                label.text = aTitle(pickerView, row, component)
            }
            else {
                label.text = items[component][row].description
            }
            
            return label
        }
    }
    
    func pickerView(_ pickerView: UIPickerView, widthForComponent component: Int) -> CGFloat {
        if let width = widthForComponent {
            return width(pickerView, component)
        }
        
        return floor(UIScreen.main.bounds.width/CGFloat(items.count))
    }
    
    func pickerView(_ pickerView: UIPickerView, rowHeightForComponent component: Int) -> CGFloat {
        if let aHeight = heightForComponent {
            return aHeight(pickerView, component)
        }
        
        return 34.0
    }
    
    init(viewForRow: ((UIPickerView, Int, Int, UIView?) -> UIView)?, widthForComponent: ((UIPickerView, Int) -> CGFloat)? = nil, heightForComponent: ((UIPickerView, Int) -> CGFloat)? = nil, titleForRow: ((UIPickerView, Int, Int) -> String)? = nil, attributedTitleForRow: ((UIPickerView, Int, Int) -> NSAttributedString)? = nil) {
        super.init()
        self.viewForRow = viewForRow
        self.widthForComponent = widthForComponent
        self.heightForComponent = heightForComponent
    }
}

扩展

Base

类型为

UIPickerView

的

Reactive

实现一个

sectionedItems

函数，与

RxCocoa

的

func items(_ source: Source) -> (_ viewForRow: @escaping (Int, Sequence.Element, UIView?) -> UIView) -> Disposable

函数类似：

extension Reactive where Base: UIPickerView {
    func sectionedItems<T: CustomStringConvertible>
        (_ source: Observable<[[T]]>)
    -> ((viewForRow: (UIPickerView, Int, Int, UIView?) -> UIView, widthForComponent: ((UIPickerView, Int) -> CGFloat)?, heightForComponent: ((UIPickerView, Int) -> CGFloat)?, titleForRow:((UIPickerView, Int, Int) -> String)?, attributedTitleForRow: ((UIPickerView, Int, Int) -> NSAttributedString)?))
    -> Disposable {
        return { arg in
            let adapter = SectionedPickerViewAdapter<T>(viewForRow: arg.0, widthForComponent: arg.1, heightForComponent: arg.2, titleForRow: arg.3, attributedTitleForRow: arg.4)
            return items(adapter: adapter)(source)
        }
    }
}

最后进行数据绑定，其绑定过程与前边分析基本一致：

Observable.just([Array(0..<10), Array(10..<100), Array(100..<1000)])
            .bind(to: centerPickerView.rx.sectionedItems, curriedArgument: ({ (_, row, component, _) in
                let label = UILabel()
                label.font = UIFont.systemFont(ofSize: 12.0)
                label.textAlignment = .center
                label.backgroundColor = UIColor.random
                label.text = data[component][row].description
                return label
            }, { _, component in
                switch component {
                case 0:
                    return 40.0
                case 1:
                    return 80.0
                default:
                    return 120.0
                }
            }, { (_, _) in 50.0 }, nil, nil))
            .disposed(by: bag)

通过前面对RxCocoa实现UIPickerView绑定的分析，也可以通过如下方式绑定数据：

let adapter = SectionedPickerViewAdapter<Int>(viewForRow: { (_, row, component, _) -> UIView in
    let label = UILabel()
    label.font = UIFont.systemFont(ofSize: 12.0)
    label.textAlignment = .center
    label.backgroundColor = UIColor.random
    label.text = data[component][row].description
    return label
}, widthForComponent: { _, component in
    switch component {
    case 0:
        return 120.0
    case 1:
        return 80.0
    default:
        return 40.0
    }
}, heightForComponent: { (_, _) in 40.0 })
Observable.just([Array(0..<10), Array(10..<100), Array(100..<1000)])
    .bind(to: bottomPickerView.rx.items(adapter: adapter))
    .disposed(by: bag)

RxSwift官方实例七（UIPickerView）

UIPickerView的Rx实现分析

RxPickerViewDelegateProxy分析

RxPickerViewDataSourceProxy分析

RxPickerViewAdapter分析

RxPickerViewArrayDataSource分析

RxPickerViewSequenceDataSource分析

RxStringPickerViewAdapter、RxAttributedStringPickerViewAdapter、RxPickerViewAdapter分析

基于UIPickerView的Reactive扩展分析

ObservableType扩展分析

UIPickerView示例

简单的绑定

数据绑定过程分析

自定义绑定

实现多组数据绑定

实现完整的数据绑定

继续阅读

吃透MVC，驯服烂代码吃透MVC，驯服烂代码

PAT (Advanced Level) Practise 1083 List Grades (25)

PAT (Advanced Level) Practise 1135 Is It A Red-Black Tree (30)

UVA 348 Optimal Array Multiplication Sequence

PAT (Advanced Level) Practise 1066 Root of AVL Tree (25)

CSU 1806 Toll

CodeChef PALPROB Palindromeness

ZOJ 1032 Area 2

UVA 590 Always on the run

FZU 1978 Repair the brackets

UVA 10344- 23 out of 5

POJ 2115 C Looooops

ZOJ 3700 Ever Dream

UVA 620 Cellular Structure

swift资料合集

苹果审核 Guideline 2.1 - Information Needed