implement NSString.stringByTrimmingCharactersInSet

Author: akolov

Foundation/NSString.swift

@@ -638,7 +638,29 @@ extension NSString {
     }
 
     public func stringByTrimmingCharactersInSet(set: NSCharacterSet) -> String {
-        NSUnimplemented()
+        let characters = _swiftObject.utf16
+        var start = characters.startIndex
+        var end = characters.endIndex
+
+        for char in characters {
+            guard set.characterIsMember(char) else {
+                break
+            }
+
+            start = start.successor()
+        }
+
+        if start < end {
+            for char in characters.suffixFrom(start).reverse() {
+                guard set.characterIsMember(char) else {
+                    break
+                }
+
+                end = end.predecessor()
+            }
+        }
+
+        return String(characters[Range<String.UTF16View.Index>(start: start, end: end)])
     }
 
     public func stringByPaddingToLength(newLength: Int, withString padString: String, startingAtIndex padIndex: Int) -> String {

TestFoundation/TestNSString.swift

@@ -32,6 +32,7 @@ class TestNSString : XCTestCase {
             ("test_FromNullTerminatedCStringInASCII", test_FromNullTerminatedCStringInASCII ),
             ("test_FromNullTerminatedCStringInUTF8", test_FromNullTerminatedCStringInUTF8 ),
             ("test_FromMalformedNullTerminatedCStringInUTF8", test_FromMalformedNullTerminatedCStringInUTF8 ),
+            ("test_stringByTrimmingCharactersInSet", test_stringByTrimmingCharactersInSet ),
         ]
     }
 
@@ -127,4 +128,27 @@ class TestNSString : XCTestCase {
         let string = NSString(CString: bytes.map { Int8(bitPattern: $0) }, encoding: NSUTF8StringEncoding)
         XCTAssertNil(string)
     }
+
+    func test_stringByTrimmingCharactersInSet() {
+        XCTAssertEqual("\u{feff}".stringByTrimmingCharactersInSet(NSCharacterSet.controlCharacterSet()), "")
+        XCTAssertEqual("a".stringByTrimmingCharactersInSet(NSCharacterSet.letterCharacterSet()), "")
+        XCTAssertEqual("a".stringByTrimmingCharactersInSet(NSCharacterSet.lowercaseLetterCharacterSet()), "")
+        XCTAssertEqual("A".stringByTrimmingCharactersInSet(NSCharacterSet.uppercaseLetterCharacterSet()), "")
+        XCTAssertEqual("\u{01c5}".stringByTrimmingCharactersInSet(NSCharacterSet.uppercaseLetterCharacterSet()), "")
+        XCTAssertEqual("\u{01c5}".stringByTrimmingCharactersInSet(NSCharacterSet.capitalizedLetterCharacterSet()), "")
+        XCTAssertEqual("\u{002b}".stringByTrimmingCharactersInSet(NSCharacterSet.symbolCharacterSet()), "")
+        XCTAssertEqual("\u{20b1}".stringByTrimmingCharactersInSet(NSCharacterSet.symbolCharacterSet()), "")
+        XCTAssertEqual("\u{000a}".stringByTrimmingCharactersInSet(NSCharacterSet.newlineCharacterSet()), "")
+        XCTAssertEqual("\u{2029}".stringByTrimmingCharactersInSet(NSCharacterSet.newlineCharacterSet()), "")
+
+        let cset1 = NSCharacterSet(charactersInString: "ABC123")
+        XCTAssertEqual("".stringByTrimmingCharactersInSet(cset1), "")
+        XCTAssertEqual("321CBA".stringByTrimmingCharactersInSet(cset1), "", "Should trim everything")
+        XCTAssertEqual("CBAabc".stringByTrimmingCharactersInSet(cset1), "abc", "Should trim only first 3 characters")
+        XCTAssertEqual("cbaABC".stringByTrimmingCharactersInSet(cset1), "cba", "Should trim only last 3 characters")
+        XCTAssertEqual("cba123abc".stringByTrimmingCharactersInSet(cset1), "cba123abc", "Should not trim anything")
+
+        let cset2 = NSCharacterSet(charactersInString: "юникодユニコード")
+        XCTAssertEqual("ЮНИゆにコドкод".stringByTrimmingCharactersInSet(cset2), "ЮНИゆに")
+    }
 }