Pure Swift extension methods for getting substrings from RegularExpressionMatch.Range and Range<Int>

Sources/RegularExpression.swift

@@ -134,3 +134,18 @@ public struct RegularExpressionMatch {
     }
 }
 
+public extension String {
+    func substring(range: RegularExpressionMatch.Range) -> String? {
+        switch range {
+        case .NotFound:
+            return nil
+        case let .Found(r):
+            return substring(r)
+        }
+    }
+
+    func substring(range: Range<Int>) -> String? {
+        let indexRange = Swift.Range(start: utf8.startIndex.advancedBy(range.startIndex), end: utf8.startIndex.advancedBy(range.endIndex))
+        return String(utf8[indexRange])
+    }
+}

SwiftFoundation/SwiftFoundation.xcodeproj/project.pbxproj

@@ -496,7 +496,9 @@
 				6E30BA1B1B40F543009B1B49 /* SwiftFoundationTests */,
 				6E30BA0E1B40F543009B1B49 /* Products */,
 			);
+			indentWidth = 4;
 			sourceTree = "<group>";
+			tabWidth = 4;
 		};
 		6E30BA0E1B40F543009B1B49 /* Products */ = {
 			isa = PBXGroup;

Tests/RegularExpressionTests.swift

@@ -93,6 +93,39 @@ class RegularExpressionTests: XCTestCase {
 
         XCTAssert(match.subexpressionRanges.count == regex.subexpressionsCount, "Subexpressions should be \(regex.subexpressionsCount), is \(match.subexpressionRanges.count)")
     }
+
+    func testEmoji() {
+
+        let testString = "🙄😒🍺🦄"
+
+        let beer = "🍺"
+
+        let pattern = "\\(\(beer)\\)"
+
+        do {
+            let beerFinder = try RegularExpression(pattern)
+
+            guard let match = beerFinder.match(testString) else {
+                XCTFail("Could not find 🍺 in \(testString)")
+                return
+            }
+
+            guard let beerRange = match.subexpressionRanges.first else {
+                XCTFail("Could not find 🍺 capture group despite \(testString) match \(match)")
+                return
+            }
+
+            guard let capturedString = testString.substring(beerRange) else {
+                XCTFail("Failed to get a substring with range \(beerRange) in \(testString)")
+                return
+            }
+
+            XCTAssertEqual(beer, capturedString, "Captured substring in \(beerRange) should match \(beer), but instead is \(capturedString)")
+        } catch {
+
+            XCTFail("Error thrown trying to create RegularExpression from \(pattern): \(error)")
+        }
+    }
 }