iOS11+: anchor.systemSpacing(_,multiplier:)

README.md

@@ -6,7 +6,7 @@
 
 Textual Auto Layout (TAL) helps you create Auto Layout constraints that you can read, understand, and maintain.
 
-In contrast to existing libraries ([SnapKit](https://github.com/SnapKit/SnapKit), [Cartography](https://github.com/robb/Cartography)), TAL follows a minimization approach. The package consists of a single ~120 lines source file, thus TAL won't have every imaginable feature. Instead you get a dependency ideal for security audits: short and tidy.
+In contrast to existing libraries ([SnapKit](https://github.com/SnapKit/SnapKit), [Cartography](https://github.com/robb/Cartography)), TAL follows a minimization approach. The package consists of a single ~150 lines source file, thus TAL won't have every imaginable feature. Instead you get a dependency ideal for security audits: short and tidy.
 
 To install, use Swift Package Manager or simply copy the source file to your project and you're good to go.
 

Sources/TextualAutoLayout/TextualAutoLayout.swift

@@ -122,3 +122,27 @@ public extension Array where Element: NSLayoutConstraint {
 		return self
 	}
 }
+
+// I couldn't find a better way to handle it, but these methods are particularly useful.
+// Sadly, the syntax isn't quite as readable as the stuff above.
+
+#if !os(macOS)
+@available(iOS 11, tvOS 11, *)
+public extension NSLayoutXAxisAnchor {
+	/// Calls and activates `.constraint(equalToSystemSpacingAfter: a)`
+	@discardableResult func systemSpacing(_ equal: NSLayoutXAxisAnchor, multiplier m: CGFloat = 1.0) -> NSLayoutConstraint { constraint(equalToSystemSpacingAfter: equal, multiplier: m).on() }
+	/// Calls and activates `.constraint(lessThanOrEqualToSystemSpacingAfter: a)`
+	@discardableResult func systemSpacing(lessThan a: NSLayoutXAxisAnchor, multiplier m: CGFloat = 1.0) -> NSLayoutConstraint { constraint(lessThanOrEqualToSystemSpacingAfter: a, multiplier: m).on() }
+	/// Calls and activates `.constraint(greaterThanOrEqualToSystemSpacingAfter: a)`
+	@discardableResult func systemSpacing(greaterThan a: NSLayoutXAxisAnchor, multiplier m: CGFloat = 1.0) -> NSLayoutConstraint { constraint(greaterThanOrEqualToSystemSpacingAfter: a, multiplier: m).on() }
+}
+@available(iOS 11, tvOS 11, *)
+public extension NSLayoutYAxisAnchor {
+	/// Calls and activates `.constraint(equalToSystemSpacingBelow: a)`
+	@discardableResult func systemSpacing(_ equal: NSLayoutYAxisAnchor, multiplier m: CGFloat = 1.0) -> NSLayoutConstraint { constraint(equalToSystemSpacingBelow: equal, multiplier: m).on() }
+	/// Calls and activates `.constraint(lessThanOrEqualToSystemSpacingBelow: a)`
+	@discardableResult func systemSpacing(lessThan a: NSLayoutYAxisAnchor, multiplier m: CGFloat = 1.0) -> NSLayoutConstraint { constraint(lessThanOrEqualToSystemSpacingBelow: a, multiplier: m).on() }
+	/// Calls and activates `.constraint(greaterThanOrEqualToSystemSpacingBelow: a)`
+	@discardableResult func systemSpacing(greaterThan a: NSLayoutYAxisAnchor, multiplier m: CGFloat = 1.0) -> NSLayoutConstraint { constraint(greaterThanOrEqualToSystemSpacingBelow: a, multiplier: m).on() }
+}
+#endif

Tests/TextualAutoLayoutTests/TextualAutoLayoutTests.swift

@@ -73,4 +73,15 @@ final class TextualAutoLayoutTests: XCTestCase {
 		x.setActive(false)
 		for u in x { XCTAssertEqual(u.isActive, false) }
 	}
+	
+	#if !os(macOS)
+	@available(iOS 11, tvOS 11, *)
+	func testSystemSpacing() {
+		let x = B.topAnchor.systemSpacing(A.bottomAnchor, multiplier: 2) | .defaultLow
+		XCTAssertEqual(x.relation, NSLayoutConstraint.Relation.equal)
+		XCTAssertEqual(x.priority, ConstraintPriority.defaultLow)
+		XCTAssertEqual(x.constant, 16)
+		XCTAssertEqual(x.multiplier, 1)
+	}
+	#endif
 }