implement NSString.boolValue

Author: jpsim

Foundation/NSString.swift

@@ -488,7 +488,16 @@ extension NSString {
 
     public var boolValue: Bool {
         get {
-            NSUnimplemented()
+            let scanner = NSScanner(string: _swiftObject)
+            // skip initial whitespace if present
+            scanner.scanCharactersFromSet(NSCharacterSet.whitespaceCharacterSet())
+            // scan a single optional '+' or '-' character, followed by zeroes
+            if scanner.scanString(string: "+") == nil {
+                scanner.scanString(string: "-")
+            }
+            // scan any following zeros
+            scanner.scanCharactersFromSet(NSCharacterSet(charactersInString: "0"))
+            return scanner.scanCharactersFromSet(NSCharacterSet(charactersInString: "tTyY123456789")) != nil
         }
     }
 

TestFoundation/TestNSString.swift

@@ -21,6 +21,7 @@ class TestNSString : XCTestCase {
 
     var allTests : [(String, () -> ())] {
         return [
+            ("test_boolValue", test_boolValue ),
             ("test_BridgeConstruction", test_BridgeConstruction ),
             ("test_isEqualToStringWithSwiftString", test_isEqualToStringWithSwiftString ),
             ("test_isEqualToObjectWithNSString", test_isEqualToObjectWithNSString ),
@@ -37,6 +38,17 @@ class TestNSString : XCTestCase {
             ("test_rangeOfCharacterFromSet", test_rangeOfCharacterFromSet ),
         ]
     }
+
+    func test_boolValue() {
+        let trueStrings: [NSString] = ["t", "true", "TRUE", "tRuE", "yes", "YES", "1", "+000009"]
+        for string in trueStrings {
+            XCTAssert(string.boolValue)
+        }
+        let falseStrings: [NSString] = ["false", "FALSE", "fAlSe", "no", "NO", "0", "<true>", "_true", "-00000"]
+        for string in falseStrings {
+            XCTAssertFalse(string.boolValue)
+        }
+    }
 
     func test_BridgeConstruction() {
         let literalConversion: NSString = "literal"