ios7新增基础类库以及OC新特性

新特性：

Modules：用XCode5新建工程默认支持modules编译，老项目需在Build Settings里查找modules，找到的Enable Modules选项设置为YES。

对应新增语法：@import，导入系统头文件，例如：@import MapKit; 或者库的部分头文件：@import UIKit.UIView;

优点：不需要再在Build Phases里的Link Binary With Libraries添加系统framework文件；缺点：不支持自定义或第三方库

新返回类型：instancetype，用在构造函数返回类型上，建议以前用id作为返回类型的都改成instancetype。

好处：有更严格的编译类型检查，便于编译时即可发现潜在的问题；

NSArray：新增函数： -(id)firstObject; 但只要ios4以上都可以用

NSData：新增Base64编码，相应的函数有：

- (id)initWithBase64EncodedString:(NSString *)base64String

      options:(NSDataBase64DecodingOptions)options;

 

- (NSString *)base64EncodedStringWithOptions:

      (NSDataBase64EncodingOptions)options;

 

- (id)initWithBase64EncodedData:(NSData *)base64Data

      options:(NSDataBase64DecodingOptions)options;

 

- (NSData *)base64EncodedDataWithOptions:

      (NSDataBase64EncodingOptions)options;

NSTimer：新增函数：

- (NSTimeInterval)tolerance;

- (void)setTolerance:(NSTimeInterval)tolerance;

设置tolerance对于启动若干个fireDate相近的NSTimer有用，节省CPU唤醒时间

NSCharacterSet新增函数：

+ (id)URLUserAllowedCharacterSet
+ (id)URLPasswordAllowedCharacterSet
+ (id)URLHostAllowedCharacterSet
+ (id)URLPathAllowedCharacterSet
+ (id)URLQueryAllowedCharacterSet
+ (id)URLFragmentAllowedCharacterSet

新增类：

NSProgress：进度通知类

NSURLComponents：可把其视作NSMutableURL，例子：

NSURLComponents *components = [NSURLComponents componentsWithString:@"http://nshipster.com"];

components.path = @"/iOS7";

components.query = @"foo=bar";

NSLog(@"%@", components.scheme); // @"http"

NSLog(@"%@", [components URL]); // @"http://nshipster.com/iOS7?foo=bar"

CIDetectorSmile & CIDetectorEyeBlink：图像微笑和眨眼识别，例子：

CIDetector *smileDetector = [CIDetector detectorOfType:CIDetectorTypeFace

                                context:context

                                options:@{CIDetectorTracking: @YES,

                                          CIDetectorAccuracy: CIDetectorAccuracyLow}];

NSArray *features = [smileDetector featuresInImage:image options:@{CIDetectorSmile:@YES}];

if (([features count] > 0) && (((CIFaceFeature *)features[0]).hasSmile)) {

    UIImageWriteToSavedPhotosAlbum(image, self, @selector(didFinishWritingImage), features);

} else {

    self.label.text = @"Say Cheese!"

}

AVCaptureMetaDataOutput：支持二维码及其他类型码识别，例子：

AVCaptureSession *session = [[AVCaptureSession alloc] init];

AVCaptureDevice *device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];

NSError *error = nil;

AVCaptureDeviceInput *input = [AVCaptureDeviceInput deviceInputWithDevice:device

                                                                    error:&error];

if (input) {

    [session addInput:input];

} else {

    NSLog(@"Error: %@", error);

}

AVCaptureMetadataOutput *output = [[AVCaptureMetadataOutput alloc] init];

[output setMetadataObjectTypes:@[AVMetadataObjectTypeQRCode]];

[output setMetadataObjectsDelegate:self queue:dispatch_get_main_queue()];

[session addOutput:output];

[session startRunning];

#pragma mark - AVCaptureMetadataOutputObjectsDelegate

- (void)captureOutput:(AVCaptureOutput *)captureOutput

didOutputMetadataObjects:(NSArray *)metadataObjects

       fromConnection:(AVCaptureConnection *)connection

{

    NSString *QRCode = nil;

    for (AVMetadataObject *metadata in metadataObjects) {

        if ([metadata.type isEqualToString:AVMetadataObjectTypeQRCode]) {

            // This will never happen; nobody has ever scanned a QR code... ever

            QRCode = [(AVMetadataMachineReadableCodeObject *)metadata stringValue];

            break;

        }

    }

    NSLog(@"QR Code: %@", QRCode);

}

SSReadingList：添加URL到safari阅读列表中，例子：

NSURL *URL = [NSURL URLWithString:@"http://nshipster.com/ios7"];

[[SSReadingList defaultReadingList] addReadingListItemWithURL:URL

                                                        title:@"NSHipster"

                                                  previewText:@"..."

                                                        error:nil];

AVSpeechSynthesizer：文本转语音，例子：

AVSpeechSynthesizer *synthesizer = [[AVSpeechSynthesizer alloc] init];

AVSpeechUtterance *utterance = [AVSpeechUtterance speechUtteranceWithString:@"Just what do you think you're doing, Dave?"];

utterance.rate = AVSpeechUtteranceMinimumSpeechRate; // Tell it to me slowly

[synthesizer speakUtterance:utterance];

MKDistanceFormatter：距离格式化为本地文本，例子：

CLLocation *sanFrancisco = [[CLLocation alloc] initWithLatitude:37.775 longitude:-122.4183333];

CLLocation *portland = [[CLLocation alloc] initWithLatitude:45.5236111 longitude:-122.675];

CLLocationDistance distance = [portland distanceFromLocation:sanFrancisco];

MKDistanceFormatter *formatter = [[MKDistanceFormatter alloc] init];

formatter.units = MKDistanceFormatterUnitsImperial;

NSLog(@"%@", [formatter stringFromDistance:distance]); // 535 miles

参考网址：
http://nshipster.com/ios7/

http://www.raywenderlich.com/49850/whats-new-in-objective-c-and-foundation-in-ios-7