Merge pull request #118 from square/entin/spread-builder

Support result builder syntax for view spreading

Paralayout/UIView+Spreading.swift

@@ -1,5 +1,5 @@
 //
-//  Copyright © 2021 Square, Inc.
+//  Copyright © 2024 Block, Inc.
 //
 //  Licensed under the Apache License, Version 2.0 (the "License");
 //  you may not use this file except in compliance with the License.
@@ -70,6 +70,35 @@ extension UIView {
 
     // MARK: - Public Methods
 
+    #if swift(>=5.4)
+    /// Sizes and positions subviews to equally take up all horizontal space.
+    ///
+    /// - precondition: The available space on the horizontal axis of the receiver's bounds must be at least as large as
+    /// the space required for the specified `margin` between each subview. In other words, the `subviews` may each have
+    /// a size of zero along the horizontal axis, but their size may not be negative.
+    ///
+    /// - parameter margin: The space between each subview.
+    /// - parameter bounds: A custom area within which to layout the subviews in the receiver's coordinate space, or
+    /// `nil` to use the receiver's `bounds`. Defaults to `nil`.
+    /// - parameter orthogonalBehavior: Controls how the view should be sized and positioned along the vertical axis.
+    /// Defaults to filling the vertical space of the `bounds`.
+    /// - parameter subviews: The subviews to spread out, ordered from the leading edge to the trailing edge of the
+    /// receiver.
+    public func horizontallySpreadSubviews(
+        margin: CGFloat,
+        inRect bounds: CGRect? = nil,
+        orthogonalBehavior: VerticalSpreadingBehavior = .fill,
+        @ViewArrayBuilder _ subviews: () -> [UIView]
+    ) {
+        horizontallySpreadSubviews(
+            subviews(),
+            margin: margin,
+            inRect: bounds,
+            orthogonalBehavior: orthogonalBehavior
+        )
+    }
+    #endif
+
     /// Sizes and positions subviews to equally take up all horizontal space.
     ///
     /// - precondition: The available space on the horizontal axis of the receiver's bounds must be at least as large as
@@ -116,6 +145,34 @@ extension UIView {
         }
     }
 
+    #if swift(>=5.4)
+    /// Sizes and positions subviews to equally take up all vertical space.
+    ///
+    /// - precondition: The available space on the vertical axis of the receiver's bounds must be at least as large as
+    /// the space required for the specified `margin` between each subview. In other words, the `subviews` may each have
+    /// a size of zero along the vertical axis, but their size may not be negative.
+    ///
+    /// - parameter margin: The space between each subview.
+    /// - parameter bounds: A custom area within which to layout the subviews in the receiver's coordinate space, or
+    /// `nil` to use the receiver's `bounds`. Defaults to `nil`.
+    /// - parameter orthogonalBehavior: Controls how the view should be sized and positioned along the horizontal axis.
+    /// Defaults to filling the horizontal space of the `bounds`.
+    /// - parameter subviews: The subviews to spread out, ordered from the top edge to the bottom edge of the receiver.
+    public func verticallySpreadSubviews(
+        margin: CGFloat,
+        inRect bounds: CGRect? = nil,
+        orthogonalBehavior: HorizontalSpreadingBehavior = .fill,
+        @ViewArrayBuilder _ subviews: () -> [UIView]
+    ) {
+        verticallySpreadSubviews(
+            subviews(),
+            margin: margin,
+            inRect: bounds,
+            orthogonalBehavior: orthogonalBehavior
+        )
+    }
+    #endif
+
     /// Sizes and positions subviews to equally take up all vertical space.
     ///
     /// - precondition: The available space on the vertical axis of the receiver's bounds must be at least as large as

Paralayout/ViewArrayBuilder.swift

@@ -0,0 +1,90 @@
+//
+//  Copyright © 2024 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.
+//
+
+import UIKit
+
+#if swift(>=5.4)
+@resultBuilder
+public struct ViewArrayBuilder {
+
+    // Build expressions, which are turned into partial results.
+
+    public static func buildExpression(_ component: UIView) -> [UIView] {
+        return [component]
+    }
+    public static func buildExpression(_ component: [UIView?]) -> [UIView] {
+        return component.compactMap { $0 }
+    }
+    public static func buildExpression(_ component: [UIView]) -> [UIView] {
+        return component
+    }
+    public static func buildExpression(_ component: UIView?) -> [UIView] {
+        return [component].compactMap { $0 }
+    }
+
+    // Build partial results, which accumulate.
+
+    public static func buildPartialBlock(first: UIView) -> [UIView] {
+        return [first]
+    }
+    public static func buildPartialBlock(first: [UIView]) -> [UIView] {
+        return first
+    }
+    public static func buildPartialBlock(accumulated: UIView, next: UIView) -> [UIView] {
+        return [accumulated, next]
+    }
+    public static func buildPartialBlock(accumulated: UIView, next: [UIView]) -> [UIView] {
+        return [accumulated] + next
+    }
+    public static func buildPartialBlock(accumulated: [UIView], next: UIView) -> [UIView] {
+        return accumulated + [next]
+    }
+    public static func buildPartialBlock(accumulated: [UIView], next: [UIView]) -> [UIView] {
+        return accumulated + next
+    }
+
+    // Build if statements
+
+    public static func buildOptional(_ component: [UIView]?) -> [UIView] {
+        return component ?? []
+    }
+    public static func buildOptional(_ component: [UIView]) -> [UIView] {
+        return component
+    }
+
+    // Build if-else and switch statements
+
+    public static func buildEither(first component: [UIView]) -> [UIView] {
+        return component
+    }
+    public static func buildEither(second component: [UIView]) -> [UIView] {
+        return component
+    }
+
+    // Build for-loop statements
+
+    public static func buildArray(_ components: [[UIView]]) -> [UIView] {
+        return components.flatMap { $0 }
+    }
+
+    // Build the blocks that turn into results.
+
+    public static func buildBlock(_ components: [UIView]...) -> [UIView] {
+        return components.flatMap { $0 }
+    }
+
+}
+#endif

ParalayoutTests/ViewArrayBuilderTests.swift

@@ -0,0 +1,194 @@
+//
+//  Copyright © 2024 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.
+//
+
+import Paralayout
+import XCTest
+
+#if swift(>=5.4)
+final class ViewArrayBuilderTests: XCTestCase {
+
+    // MARK: - Tests
+
+    func testSimpleResultBuilder() throws {
+        let view1 = UIView()
+        let view2 = UIView()
+        XCTAssertEqual(
+            viewArray {
+                view1
+                view2
+            },
+            [
+                view1,
+                view2,
+            ]
+        )
+    }
+
+    func testIfTrueResultBuilder() throws {
+        let view1 = UIView()
+        let view2 = UIView()
+        let view3 = UIView()
+        let condition = true
+        XCTAssertEqual(
+            viewArray {
+                view1
+                if condition {
+                    view2
+                }
+                view3
+            },
+            [
+                view1,
+                view2,
+                view3,
+            ]
+        )
+    }
+
+    func testIfFalseResultBuilder() throws {
+        let view1 = UIView()
+        let view2 = UIView()
+        let view3 = UIView()
+        let condition = false
+        XCTAssertEqual(
+            viewArray {
+                view1
+                if condition {
+                    view2
+                }
+                view3
+            },
+            [
+                view1,
+                view3,
+            ]
+        )
+    }
+
+    func testIfElseFirstBranchResultBuilder() throws {
+        let view1 = UIView()
+        let view2 = UIView()
+        let view3 = UIView()
+        let view4 = UIView()
+        let condition = true
+        XCTAssertEqual(
+            viewArray {
+                view1
+                if condition {
+                    view2
+                } else {
+                    view3
+                }
+                view4
+            },
+            [
+                view1,
+                view2,
+                view4,
+            ]
+        )
+    }
+
+    func testIfElseSecondBranchResultBuilder() throws {
+        let view1 = UIView()
+        let view2 = UIView()
+        let view3 = UIView()
+        let view4 = UIView()
+        let condition = false
+        XCTAssertEqual(
+            viewArray {
+                view1
+                if condition {
+                    view2
+                } else {
+                    view3
+                }
+                view4
+            },
+            [
+                view1,
+                view3,
+                view4,
+            ]
+        )
+    }
+
+    func testSwitchCaseResultBuilder() throws {
+        let view1 = UIView()
+        let view2 = UIView()
+        let view3 = UIView()
+        let value = 1
+        XCTAssertEqual(
+            viewArray {
+                view1
+                switch value {
+                case 1:
+                    view2
+                default:
+                    nil
+                }
+                view3
+            },
+            [
+                view1,
+                view2,
+                view3,
+            ]
+        )
+    }
+
+    func testSwitchDefaultResultBuilder() throws {
+        let view1 = UIView()
+        let view2 = UIView()
+        let view3 = UIView()
+        let value = 2
+        XCTAssertEqual(
+            viewArray {
+                view1
+                switch value {
+                case 1:
+                    view2
+                default:
+                    nil
+                }
+                view3
+            },
+            [
+                view1,
+                view3,
+            ]
+        )
+    }
+
+    func testForLoopResultBuilder() throws {
+        let views = [UIView(), UIView(), UIView()]
+        XCTAssertEqual(
+            viewArray {
+                for view in views {
+                    view
+                }
+            },
+            views
+        )
+    }
+
+    // MARK: - Private Methods
+
+    private func viewArray(@ViewArrayBuilder _ builder: () -> [UIView]) -> [UIView] {
+        builder()
+    }
+}
+#endif