Merge pull request #33 from iWECon/enhance

Improvement Combine, and Use UIScheduler instead safetyAccessUI

Author: iwecon

Demo/Demo/Preview1ViewController.swift

@@ -20,6 +20,7 @@ class Preview1ViewController: UIViewController {
     @Published var name = "iWECon/StackKit"
     @Published var brief = "The best way to use HStack and VStack in UIKit, and also supports Spacer and Divider."
 
+    var nameCancellable: AnyCancellable?
     var cancellables: Set<AnyCancellable> = []
 
     deinit {

README.md

@@ -30,11 +30,13 @@ HStackView(alignment: .center, distribution: .spacing(14), padding: UIEdgeInsets
 💡 There are no more examples, you can help to complete/optimize.
 
 
-### Padding
+### HStackView / VStackView
+
+Alignment, Distribution, Padding and `resultBuilder`
 
 ```swift
-HStackView(padding: UIEdgeInsets)
-VStackView(padding: UIEdgeInsets)
+HStackView(alignment: HStackAlignment, distribution: HStackDistribution, padding: UIEdgeInsets, content: @resultBuilder)
+VStackView(alignment: VStackAlignment, distribution: VStackDistribution, padding: UIEdgeInsets, content: @resultBuilder)
 ```
 
 ### Subview size is fixed
@@ -63,7 +65,7 @@ briefLabel.stack.offset(CGPoint?)
 ### SizeToFit
 
 ```swift
-briefLabel.stack.width(220).sizeToFit(.width)
+briefLabel.stack.width(220).sizeToFit(.width) // see `UIView+FitSize.swift`
 ```
 
 ### Spacer & Divider
@@ -125,6 +127,12 @@ HStackView {
 self.name = "StackKit version 1.2.3"
 // update stackView
 stackView.setNeedsLayout()
+
+// remember cleanup cancellables in deinit
+deinit {
+    // the effective same as `cancellables.forEach { $0.cancel() }`
+    cancellables.removeAll()
+}
 ```
 
 # 🤔 

Sources/StackKit/Enums.swift

@@ -2,8 +2,38 @@ import UIKit
 
 // MARK: HStack
 public enum HStackAlignment {
+    
+    /// Items are alignment top.
+    ///
+    /// |----------------------------------|
+    /// | |-------|   |------|             |
+    /// | |       |   | view2|             |
+    /// | | view1 |   |      |             |
+    /// | |       |   |------|             |
+    /// | |-------|                        |
+    /// |----------------------------------|
     case top
+    
+    /// Items are alignment center. `Default`.
+    ///
+    /// |----------------------------------|
+    /// | |-------|                        |
+    /// | |       |   |------|             |
+    /// | | view1 |   | view2|             |
+    /// | |       |   |------|             |
+    /// | |-------|                        |
+    /// |----------------------------------|
     case center
+    
+    /// Items are alignment bottom.
+    ///
+    /// |----------------------------------|
+    /// | |-------|                        |
+    /// | |       |                        |
+    /// | | view1 |   |------|             |
+    /// | |       |   | view2|             |
+    /// | |-------|   |------|             |
+    /// |----------------------------------|
     case bottom
 }
 
@@ -25,8 +55,44 @@ public enum HStackDistribution {
 
 // MARK: - VStack
 public enum VStackAlignment {
+    
+    /// Items are alignment left.
+    ///
+    /// |----------------------|
+    /// | |----------------|   |
+    /// | |    view1       |   |
+    /// | |----------------|   |
+    /// |                      |
+    /// | |---------|          |
+    /// | |  view2  |          |
+    /// | |---------|          |
+    /// |----------------------|
     case left
+    
+    /// Items are alignment center. `Default`.
+    ///
+    /// |----------------------|
+    /// |  |----------------|  |
+    /// |  |      view1     |  |
+    /// |  |----------------|  |
+    /// |                      |
+    /// |     |----------|     |
+    /// |     |  view2   |     |
+    /// |     |----------|     |
+    /// |----------------------|
     case center
+    
+    /// Items are alignment right.
+    ///
+    /// |----------------------|
+    /// |   |----------------| |
+    /// |   |      view1     | |
+    /// |   |----------------| |
+    /// |                      |
+    /// |         |----------| |
+    /// |         |  view2   | |
+    /// |         |----------| |
+    /// |----------------------|
     case right
 }
 

Sources/StackKit/UIView+StackKit/UIView+Combine.swift

@@ -8,16 +8,68 @@
 import UIKit
 import Combine
 
-fileprivate func safetyAccessUI(_ closure: @escaping () -> Void) {
-    if Thread.isMainThread {
-        closure()
-    } else {
-        DispatchQueue.main.async {
-            closure()
+/// Safety Access UI.
+///
+/// A scheduler that performs all work on the main queue, as soon as possible.
+///
+/// If the caller is already running on the main queue when an action is
+/// scheduled, it may be run synchronously. However, ordering between actions
+/// will always be preserved.
+fileprivate final class UIScheduler {
+    private static let dispatchSpecificKey = DispatchSpecificKey<UInt8>()
+    private static let dispatchSpecificValue = UInt8.max
+    private static var __once: () = {
+            DispatchQueue.main.setSpecific(key: UIScheduler.dispatchSpecificKey,
+                                           value: dispatchSpecificValue)
+    }()
+    
+    private let queueLength: UnsafeMutablePointer<Int32> = {
+        let memory = UnsafeMutablePointer<Int32>.allocate(capacity: 1)
+        memory.initialize(to: 0)
+        return memory
+    }()
+    
+    deinit {
+        queueLength.deinitialize(count: 1)
+        queueLength.deallocate()
+    }
+    
+    init() {
+        /// This call is to ensure the main queue has been setup appropriately
+        /// for `UIScheduler`. It is only called once during the application
+        /// lifetime, since Swift has a `dispatch_once` like mechanism to
+        /// lazily initialize global variables and static variables.
+        _ = UIScheduler.__once
+    }
+    
+    /// Queues an action to be performed on main queue. If the action is called
+    /// on the main thread and no work is queued, no scheduling takes place and
+    /// the action is called instantly.
+    func schedule(_ action: @escaping () -> Void) {
+        let positionInQueue = enqueue()
+        
+        // If we're already running on the main queue, and there isn't work
+        // already enqueued, we can skip scheduling and just execute directly.
+        if positionInQueue == 1, DispatchQueue.getSpecific(key: UIScheduler.dispatchSpecificKey) == UIScheduler.dispatchSpecificValue {
+            action()
+            dequeue()
+        } else {
+            DispatchQueue.main.async {
+                defer { self.dequeue() }
+                action()
+            }
         }
     }
+    
+    private func dequeue() {
+        OSAtomicDecrement32(queueLength)
+    }
+    private func enqueue() -> Int32 {
+        OSAtomicIncrement32(queueLength)
+    }
 }
 
+
 @available(iOS 13.0, *)
 extension StackKitCompatible where Base: UIView {
 
@@ -35,6 +87,21 @@ extension StackKitCompatible where Base: UIView {
         }.store(in: &cancellables)
         return self
     }
+    
+    @discardableResult
+    public func receive<Value>(
+        publisher: Published<Value>.Publisher,
+        cancellable: inout AnyCancellable?,
+        sink receiveValue: @escaping ((Base, Published<Value>.Publisher.Output) -> Void)
+    ) -> Self
+    {
+        let v = self.view
+        cancellable = publisher.sink(receiveValue: { [weak v] output in
+            guard let v else { return }
+            receiveValue(v, output)
+        })
+        return self
+    }
 
     @discardableResult
     public func receive(
@@ -43,26 +110,28 @@ extension StackKitCompatible where Base: UIView {
     ) -> Self
     {
         receive(publisher: publisher, storeIn: &cancellables) { view, output in
-            safetyAccessUI {
+            UIScheduler().schedule {
+                view.isHidden = output
+            }
+        }
+        return self
+    }
+    
+    @discardableResult
+    public func receive(
+        isHidden publisher: Published<Bool>.Publisher,
+        cancellable: inout AnyCancellable?
+    ) -> Self
+    {
+        receive(publisher: publisher, cancellable: &cancellable) { view, output in
+            UIScheduler().schedule {
                 view.isHidden = output
             }
         }
         return self
     }
 }
 
-/**
- 这里由于设计逻辑，会有个问题
- 
- 系统提供的 receive(on: DispatchQueue.main) 虽然也可以
-    ⚠️ 但是：DispatchQueue 是个调度器
- 任务添加后需要等到下一个 loop cycle 才会执行
- 这样就会导致一个问题：
-    ❌ 在主线程中修改值，并触发 `container.setNeedsLayout()` 的时候，
- `setNeedsLayout` 会先执行，而 `publisher` 会将任务派发到下一个 loop cycle (也就是 setNeedsLayout 和 receive 先后执行的问题)
- 所以这里采用 `safetyAccessUI` 来处理线程问题
- */
-
 @available(iOS 13.0, *)
 extension StackKitCompatible where Base: UILabel {
 
@@ -73,7 +142,20 @@ extension StackKitCompatible where Base: UILabel {
     ) -> Self
     {
         receive(publisher: publisher, storeIn: &cancellables) { view, output in
-            safetyAccessUI {
+            UIScheduler().schedule {
+                view.text = output
+            }
+        }
+    }
+    
+    @discardableResult
+    public func receive(
+        text publisher: Published<String>.Publisher,
+        cancellable: inout AnyCancellable?
+    ) -> Self
+    {
+        receive(publisher: publisher, cancellable: &cancellable) { view, output in
+            UIScheduler().schedule {
                 view.text = output
             }
         }
@@ -87,7 +169,20 @@ extension StackKitCompatible where Base: UILabel {
     ) -> Self
     {
         receive(publisher: publisher, storeIn: &cancellables) { view, output in
-            safetyAccessUI {
+            UIScheduler().schedule {
+                view.text = output
+            }
+        }
+    }
+    
+    @discardableResult
+    public func receive(
+        text publisher: Published<String?>.Publisher,
+        cancellable: inout AnyCancellable?
+    ) -> Self
+    {
+        receive(publisher: publisher, cancellable: &cancellable) { view, output in
+            UIScheduler().schedule {
                 view.text = output
             }
         }
@@ -100,7 +195,20 @@ extension StackKitCompatible where Base: UILabel {
     ) -> Self
     {
         receive(publisher: publisher, storeIn: &cancellables) { view, output in
-            safetyAccessUI {
+            UIScheduler().schedule {
+                view.attributedText = output
+            }
+        }
+    }
+    
+    @discardableResult
+    public func receive(
+        attributedText publisher: Published<NSAttributedString>.Publisher,
+        cancellable: inout AnyCancellable?
+    ) -> Self
+    {
+        receive(publisher: publisher, cancellable: &cancellable) { view, output in
+            UIScheduler().schedule {
                 view.attributedText = output
             }
         }
@@ -113,10 +221,22 @@ extension StackKitCompatible where Base: UILabel {
     ) -> Self
     {
         receive(publisher: publisher, storeIn: &cancellables) { view, output in
-            safetyAccessUI {
+            UIScheduler().schedule {
                 view.attributedText = output
             }
         }
     }
 
+    @discardableResult
+    public func receive(
+        attributedText publisher: Published<NSAttributedString?>.Publisher,
+        cancellable: inout AnyCancellable?
+    ) -> Self
+    {
+        receive(publisher: publisher, cancellable: &cancellable) { view, output in
+            UIScheduler().schedule {
+                view.attributedText = output
+            }
+        }
+    }
 }