ios7 新特性库
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：
01.
- (id)initWithBase64EncodedString:(NSString *)base64String
02.
options:(NSDataBase64DecodingOptions)options;
03.
04.
- (NSString *)base64EncodedStringWithOptions:
05.
(NSDataBase64EncodingOptions)options;
06.
07.
- (id)initWithBase64EncodedData:(NSData *)base64Data
08.
options:(NSDataBase64DecodingOptions)options;
09.
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- (NSData *)base64EncodedDataWithOptions:
11.
(NSDataBase64EncodingOptions)options;
NSTimer：新增函数：
1.
- (NSTimeInterval)tolerance;
2.
- (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：
1.
+ (id)URLUserAllowedCharacterSet
2.
+ (id)URLPass<a href="http://www.it165.net/edu/ebg/" target="_blank" class="keylink">word</a>AllowedCharacterSet
3.
+ (id)URLHostAllowedCharacterSet
4.
+ (id)URLPathAllowedCharacterSet
5.
+ (id)URLQueryAllowedCharacterSet
6.
+ (id)URLFragmentAllowedCharacterSet
新增类：
NSProgress：进度通知类
NSURLComponents：可把其视作NSMutableURL，例子：
1.
NSURLComponents *components = [NSURLComponents componentsWithString:@"http://nshipster.com"];
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components.path = @"/iOS7";
3.
components.query = @"foo=bar";
4.
5.
NSLog(@"%@", components.scheme); // @"http"
6.
NSLog(@"%@", [components URL]); // @http://nshipster.com/iOS7?foo=bar
CIDetectorSmile & CIDetectorEyeBlink：图像微笑和眨眼识别，例子：
01.
CIDetector *smileDetector = [CIDetector detectorOfType:CIDetectorTypeFace
02.
context:context
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options:@{CIDetectorTracking: @YES,
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CIDetectorAccuracy: CIDetectorAccuracyLow}];
05.
NSArray *features = [smileDetector featuresInImage:image options:@{CIDetectorSmile:@YES}];
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if (([features count] > 0) && (((CIFaceFeature *)features[0]).hasSmile)) {
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UIImageWriteToSavedPhotosAlbum(image, self, @selector(didFinishWritingImage), features);
08.
} else {
09.
self.label.text = @"Say Cheese!"
10.
}
AVCaptureMetaDataOutput：支持二维码及其他类型码识别，例子：
01.
AVCaptureSession *session = [[AVCaptureSession alloc] init];
02.
AVCaptureDevice *device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
03.
NSError *error = nil;
04.
05.
AVCaptureDeviceInput *input = [AVCaptureDeviceInput deviceInputWithDevice:device
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error:&error];
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if (input) {
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[session addInput:input];
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} else {
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NSLog(@"Error: %@", error);
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}
12.
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AVCaptureMetadataOutput *output = [[AVCaptureMetadataOutput alloc] init];
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[output setMetadataObjectTypes:@[AVMetadataObjectTypeQRCode]];
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[output setMetadataObjectsDelegate:self queue:dispatch_get_main_queue()];
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[session addOutput:output];
17.
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[session startRunning];
01.
#pragma mark - AVCaptureMetadataOutputObjectsDelegate
02.
03.
- (void)captureOutput:(AVCaptureOutput *)captureOutput
04.
didOutputMetadataObjects:(NSArray *)metadataObjects
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fromConnection:(AVCaptureConnection *)connection
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{
07.
NSString *QRCode = nil;
08.
for (AVMetadataObject *metadata in metadataObjects) {
09.
if ([metadata.type isEqualToString:AVMetadataObjectTypeQRCode]) {
10.
// This will never happen; nobody has ever scanned a QR code... ever
11.
QRCode = [(AVMetadataMachineReadableCodeObject *)metadata stringValue];
12.
break;
13.
}
14.
}
15.
16.
NSLog(@"QR Code: %@", QRCode);
17.
}
SSReadingList：添加URL到safari阅读列表中，例子：
1.
NSURL *URL = [NSURL URLWithString:@"http://nshipster.com/ios7"];
2.
[[SSReadingList defaultReadingList] addReadingListItemWithURL:URL
3.
title:@"NSHipster"
4.
previewText:@"..."
5.
error:nil];
AVSpeechSynthesizer：文本转语音，例子：
1.
AVSpeechSynthesizer *synthesizer = [[AVSpeechSynthesizer alloc] init];
2.
AVSpeechUtterance *utterance = [AVSpeechUtterance speechUtteranceWithString:@"Just what do you think you're doing, Dave?"];
3.
utterance.rate = AVSpeechUtteranceMinimumSpeechRate; // Tell it to me slowly
4.
[synthesizer speakUtterance:utterance];
MKDistanceFormatter：距离格式化为本地文本，例子：
1.
CLLocation *sanFrancisco = [[CLLocation alloc] initWithLatitude:37.775 longitude:-122.4183333];
2.
CLLocation *portland = [[CLLocation alloc] initWithLatitude:45.5236111 longitude:-122.675];
3.
CLLocationDistance distance = [portland distanceFromLocation:sanFrancisco];
4.
5.
MKDistanceFormatter *formatter = [[MKDistanceFormatter alloc] init];
6.
formatter.units = MKDistanceFormatterUnitsImperial;
7.
NSLog(@"%@", [formatter stringFromDistance:distance]); // 535 miles