Add multiplier argument to NSLayoutDimension (#350)

* Add multiplier argument to NSLayoutDimension

* Update cheatsheet

* Add documentation

Sources/Layout/UIKit/NSLayoutDimension.swift

@@ -18,23 +18,25 @@ extension NSLayoutDimension {
     /// - Parameters:
     ///   - relation: The relationship between the receiver and the dimension anchor.
     ///   - anchor: The anchor to which to constrain.
+    ///   - multiplier: The multiplier for the constraint.
     ///   - constant: The offset for the constraint.
     ///
     /// - Returns: The created constraint.
     public func constraint(
         is relation: NSLayoutConstraint.Relation = .equal,
         to anchor: NSLayoutDimension,
+        multiplier: CGFloat = 1,
         constant: CGFloat = 0
     ) -> NSLayoutConstraint {
         switch relation {
         case .equal:
-            return constraint(equalTo: anchor, constant: constant)
+            return constraint(equalTo: anchor, multiplier: multiplier, constant: constant)
         case .greaterThanOrEqual:
-            return constraint(greaterThanOrEqualTo: anchor, constant: constant)
+            return constraint(greaterThanOrEqualTo: anchor, multiplier: multiplier, constant: constant)
         case .lessThanOrEqual:
-            return constraint(lessThanOrEqualTo: anchor, constant: constant)
+            return constraint(lessThanOrEqualTo: anchor, multiplier: multiplier, constant: constant)
         @unknown default:
-            return constraint(equalTo: anchor, constant: constant)
+            return constraint(equalTo: anchor, multiplier: multiplier, constant: constant)
         }
     }
 

Tests/LayoutTests/UIKit/NSLayoutDimensionTests.swift

@@ -14,7 +14,7 @@ import XCTest
 @MainActor
 final class NSLayoutDimensionTests: XCTestCase {
 
-    func testConstraintIsRelationToAnchorConstant_givenDefaults() {
+    func testConstraintIsRelationToAnchorMultiplierConstant_givenDefaults() {
 
         // GIVEN
 
@@ -35,7 +35,28 @@ final class NSLayoutDimensionTests: XCTestCase {
         expect(constraint).to(match(expected))
     }
 
-    func testConstraintIsRelationToAnchorConstant_givenConstant() {
+    func testConstraintIsRelationToAnchorMultiplierConstant_givenMultiplier() {
+
+        // GIVEN
+
+        let viewA: UIView = .init()
+        let viewB: UIView = .init()
+        let expected: NSLayoutConstraint = viewA
+            .width
+            .constraint(equalTo: viewB.width, multiplier: 23)
+
+        // WHEN
+
+        let constraint: NSLayoutConstraint = viewA
+            .width
+            .constraint(to: viewB.width, multiplier: 23)
+
+        // THEN
+
+        expect(constraint).to(match(expected))
+    }
+
+    func testConstraintIsRelationToAnchorMultiplierConstant_givenConstant() {
 
         // GIVEN
 
@@ -56,7 +77,7 @@ final class NSLayoutDimensionTests: XCTestCase {
         expect(constraint).to(match(expected))
     }
 
-    func testConstraintIsRelationToAnchorConstant_givenGreaterThanOrEqualRelation() {
+    func testConstraintIsRelationToAnchorMultiplierConstant_givenGreaterThanOrEqualRelation() {
 
         // GIVEN
 
@@ -77,7 +98,7 @@ final class NSLayoutDimensionTests: XCTestCase {
         expect(constraint).to(match(expected))
     }
 
-    func testConstraintIsRelationToAnchorConstant_givenLessThanOrEqualRelation() {
+    func testConstraintIsRelationToAnchorMultiplierConstant_givenLessThanOrEqualRelation() {
 
         // GIVEN
 

cheatsheet.html

@@ -354,6 +354,7 @@ <h3>NSLayoutDimension</h3>
                         <pre>constraint(to: view.width)</pre>
                         <pre>constraint(is: .greaterThanOrEqual,
            to: view.width,
+           multiplier: 2,
            constant: 100)</pre>
                         <pre>constraint(is: .greaterThanOrEqual,
            to: 100)</pre>