implement NSString.boolValue

Author: jpsim

Foundation/NSString.swift

@@ -459,7 +459,12 @@ extension NSString {
 
     public var boolValue: Bool {
         get {
-            NSUnimplemented()
+            for prefix in ["t", "y", "T", "Y", "1", "2", "3", "4", "5", "6", "7", "8", "9"] {
+                if _swiftObject.hasPrefix(prefix) {
+                    return true
+                }
+            }
+            return false
         }
     }
 

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_FromASCIIData", test_FromASCIIData ),
@@ -34,6 +35,17 @@ class TestNSString : XCTestCase {
             ("test_FromMalformedNullTerminatedCStringInUTF8", test_FromMalformedNullTerminatedCStringInUTF8 ),
         ]
     }
+
+    func test_boolValue() {
+        let trueStrings: [NSString] = ["t", "true", "TRUE", "tRuE", "yes", "YES", "1"]
+        for string in trueStrings {
+            XCTAssert(string.boolValue)
+        }
+        let falseStrings: [NSString] = ["false", "FALSE", "fAlSe", "no", "NO", "0", "<true>", "_true"]
+        for string in falseStrings {
+            XCTAssertFalse(string.boolValue)
+        }
+    }
 
     func test_BridgeConstruction() {
         let literalConversion: NSString = "literal"