Remake UIStackViewElement into UIStackViewConfiguration for more flexibility

Author: Ernest0-Production

Sources/DeclarativeLayoutKit/AutoLayout/AutoLayoutItem.swift

@@ -8,13 +8,16 @@
 import UIKit
 
 
-public protocol AutoLayoutItemConvertible: UIStackViewElementConvertable {
+public protocol AutoLayoutItemConvertible: UIStackViewConfiguration {
     func asAutoLayoutItem() -> AutoLayoutItem
 }
 
 extension AutoLayoutItemConvertible {
-    public func asUIStackViewElement() -> UIStackViewElement {
-        UIStackViewElement.arranged(self)
+    public func configure(stackView: UIStackView) {
+        let item = self.asAutoLayoutItem()
+        stackView.addArrangedSubview(item.view)
+        item.move(to: stackView)
+        item.activate()
     }
 }
 

Sources/DeclarativeLayoutKit/Helpers/KVO.swift

@@ -0,0 +1,27 @@
+//
+//  File.swift
+//  
+//
+//  Created by Ernest Babayan on 04.07.2021.
+//
+
+import Foundation
+
+private final class DeallocObserver {
+    private let completion: () -> Void
+    
+    @discardableResult
+    fileprivate init(
+        _ object: AnyObject,
+        _ completion: @escaping () -> Void
+    ) {
+        self.completion = completion
+        objc_setAssociatedObject(object, "DeallocObserver", self, .OBJC_ASSOCIATION_RETAIN)
+    }
+    
+    deinit { completion() }
+}
+
+func whenDeallocated(_ object: AnyObject, _ completion: @escaping () -> Void) {
+    DeallocObserver(object, completion)
+}

Sources/DeclarativeLayoutKit/StackView/UIStackViewBuilder.swift

@@ -10,7 +10,7 @@ import UIKit
 
 public extension UIStackView {
     /// Reset arrangedSubiews
-    func set(elements: [UIStackViewElementConvertable]) {
+    func set(elements: [UIStackViewConfiguration]) {
         for subview in arrangedSubviews {
             removeArrangedSubview(subview)
             subview.removeFromSuperview()
@@ -19,31 +19,9 @@ public extension UIStackView {
         append(elements: elements)
     }
 
-    func append(elements: [UIStackViewElementConvertable]) {
+    func append(elements: [UIStackViewConfiguration]) {
         for element in elements {
-            switch element.asUIStackViewElement() {
-            case UIStackViewElement.space(let space):
-                guard let view = arrangedSubviews.last else {
-                    assertionFailure("You cannot add a space before the first arranged view")
-                    continue
-                }
-                
-                var finalSpace = space
-                
-                let currentSpaces = customSpacing(after: view)
-                let systemSpaces = [UIStackView.spacingUseDefault, UIStackView.spacingUseSystem]
-                if !systemSpaces.contains(currentSpaces) {
-                    finalSpace += currentSpaces
-                }
-                
-                setCustomSpacing(finalSpace, after: view)
-                
-            case UIStackViewElement.arranged(let itemBox):
-                let item = itemBox.asAutoLayoutItem()
-                addArrangedSubview(item.view)
-                item.move(to: self)
-                item.activate()
-            }
+            element.configure(stackView: self)
         }
     }
 }

Sources/DeclarativeLayoutKit/StackView/UIStackViewConfiguration.swift

@@ -0,0 +1,25 @@
+//
+//  File.swift
+//  
+//
+//  Created by Ernest Babayan on 05.06.2021.
+//
+
+import UIKit
+
+
+public protocol UIStackViewConfiguration {
+    func configure(stackView: UIStackView)
+}
+
+public struct AnyUIStackViewConfiguration: UIStackViewConfiguration {
+    public init(_ configuration: @escaping (UIStackView) -> Void) {
+        self.configuration = configuration
+    }
+    
+    let configuration: (UIStackView) -> Void
+    
+    public func configure(stackView: UIStackView) {
+        configuration(stackView)
+    }
+}

Sources/DeclarativeLayoutKit/StackView/UIStackViewElement.swift

@@ -8,105 +8,105 @@
 import UIKit
 
 
-public typealias ArrangedViewsBuilder = ArrayBuilder<UIStackViewElementConvertable>
+public typealias StackViewConfigurationsComposer = ArrayBuilder<UIStackViewConfiguration>
 
 
 public extension UIStackView {
     @discardableResult
-    func set(@ArrangedViewsBuilder _ elements: () -> [UIStackViewElementConvertable]) -> Self {
+    func set(@StackViewConfigurationsComposer _ elements: () -> [UIStackViewConfiguration]) -> Self {
         set(elements: elements())
         return self
     }
 
     @discardableResult
-    func append(@ArrangedViewsBuilder _ elements: () -> [UIStackViewElementConvertable]) -> Self {
+    func append(@StackViewConfigurationsComposer _ elements: () -> [UIStackViewConfiguration]) -> Self {
         append(elements: elements())
         return self
     }
 }
 
 // MARK: - Horizontal
 
-public func HorizontalStack(_ elements: [UIStackViewElementConvertable]) -> UIStackView {
+public func HorizontalStack(_ elements: [UIStackViewConfiguration]) -> UIStackView {
     let stack = UIStackView()
     stack.axis = NSLayoutConstraint.Axis.horizontal
     stack.append(elements: elements)
     return stack
 }
 
-public func HorizontalStack(@ArrangedViewsBuilder _ elements: () -> [UIStackViewElementConvertable]) -> UIStackView {
+public func HorizontalStack(@StackViewConfigurationsComposer _ elements: () -> [UIStackViewConfiguration]) -> UIStackView {
     HorizontalStack(elements())
 }
 
-public func TopStack(_ elements: [UIStackViewElementConvertable]) -> UIStackView {
+public func TopStack(_ elements: [UIStackViewConfiguration]) -> UIStackView {
     let stack = HorizontalStack(elements)
     stack.alignment = .top
     return stack
 }
 
-public func TopStack(@ArrangedViewsBuilder _ elements: () -> [UIStackViewElementConvertable]) -> UIStackView {
+public func TopStack(@StackViewConfigurationsComposer _ elements: () -> [UIStackViewConfiguration]) -> UIStackView {
     TopStack(elements())
 }
 
-public func BottomStack(_ elements: [UIStackViewElementConvertable]) -> UIStackView {
+public func BottomStack(_ elements: [UIStackViewConfiguration]) -> UIStackView {
     let stack = HorizontalStack(elements)
     stack.alignment = .bottom
     return stack
 }
 
-public func BottomStack(@ArrangedViewsBuilder _ elements: () -> [UIStackViewElementConvertable]) -> UIStackView {
+public func BottomStack(@StackViewConfigurationsComposer _ elements: () -> [UIStackViewConfiguration]) -> UIStackView {
     BottomStack(elements())
 }
 
-public func HorizontalCenterStack(_ elements: [UIStackViewElementConvertable]) -> UIStackView {
+public func HorizontalCenterStack(_ elements: [UIStackViewConfiguration]) -> UIStackView {
     let stack = HorizontalStack(elements)
     stack.alignment = .center
     return stack
 }
 
-public func HorizontalCenterStack(@ArrangedViewsBuilder _ elements: () -> [UIStackViewElementConvertable]) -> UIStackView {
+public func HorizontalCenterStack(@StackViewConfigurationsComposer _ elements: () -> [UIStackViewConfiguration]) -> UIStackView {
     HorizontalCenterStack(elements())
 }
 
 // MARK: - Vertical
 
-public func VerticalStack(_ elements: [UIStackViewElementConvertable]) -> UIStackView {
+public func VerticalStack(_ elements: [UIStackViewConfiguration]) -> UIStackView {
     let stack = UIStackView()
     stack.axis = NSLayoutConstraint.Axis.vertical
     stack.append(elements: elements)
     return stack
 }
 
-public func VerticalStack(@ArrangedViewsBuilder _ elements: () -> [UIStackViewElementConvertable]) -> UIStackView {
+public func VerticalStack(@StackViewConfigurationsComposer _ elements: () -> [UIStackViewConfiguration]) -> UIStackView {
     VerticalStack(elements())
 }
 
-public func LeftStack(_ elements: [UIStackViewElementConvertable]) -> UIStackView {
+public func LeftStack(_ elements: [UIStackViewConfiguration]) -> UIStackView {
     let stack = VerticalStack(elements)
     stack.alignment = .leading
     return stack
 }
 
-public func LeftStack(@ArrangedViewsBuilder _ elements: () -> [UIStackViewElementConvertable]) -> UIStackView {
+public func LeftStack(@StackViewConfigurationsComposer _ elements: () -> [UIStackViewConfiguration]) -> UIStackView {
     LeftStack(elements())
 }
 
-public func RightStack(_ elements: [UIStackViewElementConvertable]) -> UIStackView {
+public func RightStack(_ elements: [UIStackViewConfiguration]) -> UIStackView {
     let stack = VerticalStack(elements)
     stack.alignment = .trailing
     return stack
 }
 
-public func RightStack(@ArrangedViewsBuilder _ elements: () -> [UIStackViewElementConvertable]) -> UIStackView {
+public func RightStack(@StackViewConfigurationsComposer _ elements: () -> [UIStackViewConfiguration]) -> UIStackView {
     RightStack(elements())
 }
 
-public func VerticalCenterStack(_ elements: [UIStackViewElementConvertable]) -> UIStackView {
+public func VerticalCenterStack(_ elements: [UIStackViewConfiguration]) -> UIStackView {
     let stack = VerticalStack(elements)
     stack.alignment = .center
     return stack
 }
 
-public func VerticalCenterStack(@ArrangedViewsBuilder _ elements: () -> [UIStackViewElementConvertable]) -> UIStackView {
+public func VerticalCenterStack(@StackViewConfigurationsComposer _ elements: () -> [UIStackViewConfiguration]) -> UIStackView {
     VerticalCenterStack(elements())
 }

Sources/DeclarativeLayoutKit/StackView/UIStackViewHelpers.swift

@@ -0,0 +1,89 @@
+//
+//  File.swift
+//  
+//
+//  Created by Ernest Babayan on 04.07.2021.
+//
+
+import UIKit
+
+
+public func UIStackViewSpace(_ value: CGFloat, withSummation: Bool = false) -> UIStackViewConfiguration {
+    AnyUIStackViewConfiguration { (stackView: UIStackView) in
+        let view = stackView.lastArrangedView
+        
+        var finalSpace = value
+        
+        if withSummation {
+            let currentSpaces = stackView.customSpacing(after: view)
+            
+            if !UIStackView.systemSpaces.contains(currentSpaces) {
+                finalSpace += currentSpaces
+            }
+        }
+        
+        stackView.setCustomSpacing(finalSpace, after: view)
+    }
+}
+public func UIStackViewSpace(_ value: CGFloat, bindVisibilityTo view: UIView) -> UIStackViewConfiguration {
+    AnyUIStackViewConfiguration { [weak view] (stackView: UIStackView) in
+        guard let view = view else { return }
+        
+        let subscription = view.observe(
+            \.isHidden,
+            
+            options: [.initial, .new],
+            
+            changeHandler: { [weak stackView] view, change in
+                guard let isHidden = change.newValue else { return }
+                
+                stackView?.setCustomSpacing(
+                    isHidden ? UIStackView.spacingUseDefault : value,
+                    after: view
+                )
+            })
+        
+        whenDeallocated(view, subscription.invalidate)
+    }
+}
+
+public typealias UIStackViewSpaceObserver = (CGFloat) -> Void
+public typealias UIStackViewSpaceProvider = (UIStackViewSpaceObserver) -> Void
+
+public func UIStackViewSpace(dynamic provider: @escaping UIStackViewSpaceProvider) -> UIStackViewConfiguration {
+    AnyUIStackViewConfiguration { (stackView: UIStackView) in
+        let view = stackView.lastArrangedView
+        
+        provider({ [weak stackView, weak view] (newSpace: CGFloat) in
+            guard let view = view else { return }
+            
+            stackView?.setCustomSpacing(newSpace, after: view)
+        })
+    }
+}
+
+private extension UIStackView {
+    var lastArrangedView: UIView {
+        guard let view = arrangedSubviews.last else {
+            preconditionFailure("You cannot add a space before the first arranged view")
+        }
+        
+        return view
+    }
+    
+    static let systemSpaces = [UIStackView.spacingUseDefault, UIStackView.spacingUseSystem]
+    
+    func observeArrangedSubviews(_ observer: @escaping ([UIView]) -> Void) {
+        let subscription = layer.observe(
+            \.sublayers,
+            
+            options: [.initial, .new],
+            
+            changeHandler: { [unowned self] _, _ in
+                observer(arrangedSubviews)
+            }
+        )
+        
+        whenDeallocated(self, subscription.invalidate)
+    }
+}