前言
在IOS7之前一般语音识别是靠一些第三方库，iOS7之后，苹果提供了文字转语音的API可以使用。
导入框架
导入AVFoundation框架：
#import <AVFoundation/AVFoundation.h>
用法详解
所用的类，主要有三个AVSpeechSynthesizer（声音合成器，控制播放，暂定，继续，停止等），AVSpeechUtterance（表达器，控制内容，音调，速率等），AVSpeechSynthesisVoice（语言）。
1：AVSpeechSynthesizer
//开始,传入AVSpeechUtterance参数
- (void)speakUtterance:(AVSpeechUtterance *)utterance;
//停止
- (BOOL)stopSpeakingAtBoundary:(AVSpeechBoundary)boundary;
typedef NS_ENUM(NSInteger, AVSpeechBoundary) {
AVSpeechBoundaryImmediate,//立即停止
AVSpeechBoundaryWord //读完最后一个词停止
}
//暂停
- (BOOL)pauseSpeakingAtBoundary:(AVSpeechBoundary)boundary;
//继续
- (BOOL)continueSpeaking;
2:AVSpeechUtterance
//初始化
+ (instancetype)speechUtteranceWithString:(NSString *)string;
+ (instancetype)speechUtteranceWithAttributedString:(NSAttributedString *)string NS_AVAILABLE_IOS(10_0);
- (instancetype)initWithString:(NSString *)string;
- (instancetype)initWithAttributedString:(NSAttributedString *)string NS_AVAILABLE_IOS(10_0);
//属性
@property(nonatomic, retain, nullable) AVSpeechSynthesisVoice *voice;//声音
@property(nonatomic, readonly) NSString *speechString;//内容字符串
@property(nonatomic, readonly) NSAttributedString *attributedSpeechString NS_AVAILABLE_IOS(10_0);//内容富文本
@property(nonatomic) float rate; // 速率AVSpeechUtteranceMinimumSpeechRate 之间 AVSpeechUtteranceMaximumSpeechRate.
@property(nonatomic) float pitchMultiplier; // 音调0.5-2
@property(nonatomic) float volume; // 音量0-1
@property(nonatomic) NSTimeInterval preUtteranceDelay; //每句前延迟时间 默认0
@property(nonatomic) NSTimeInterval postUtteranceDelay; // 美剧后延迟时间 默认0
3：AVSpeechSynthesisVoice
+ (NSArray*)speechVoices;//所有语言
+ (NSString *)currentLanguageCode;//当前语言
+ (nullable AVSpeechSynthesisVoice *)voiceWithLanguage:(nullable NSString *)languageCode;//通过languageCode初始化
支持语言：(可通过speechVoices获取所有，currentLanguageCode获取当前）
Arabic (ar-SA)
Chinese (zh-CN, zh-HK, zh-TW)
Czech (cs-CZ)
Danish (da-DK)
Dutch (nl-BE, nl-NL)
English (en-AU, en-GB, en-IE, en-US, en-ZA)
Finnish (fi-FI)
French (fr-CA, fr-FR)
German (de-DE)
Greek (el-GR)
Hebrew (he-IL)
Hindi (hi-IN)
Hungarian (hu-HU)
Indonesian (id-ID)
Italian (it-IT)
Japanese (ja-JP)
Korean (ko-KR)
Norwegian (no-NO)
Polish (pl-PL)
Portuguese (pt-BR, pt-PT)
Romanian (ro-RO)
Russian (ru-RU)
Slovak (sk-SK)
Spanish (es-ES, es-MX)
Swedish (sv-SE)
Thai (th-TH)
Turkish (tr-TR)
+ (nullable AVSpeechSynthesisVoice *)voiceWithIdentifier:(NSString *)identifier NS_AVAILABLE_IOS(9_0);//通过identifier初始化
4：AVSpeechSynthesizerDelegate（控制状态完成操作）
//开始执行
- (void)speechSynthesizer:(AVSpeechSynthesizer *)synthesizer didStartSpeechUtterance:(AVSpeechUtterance *)utterance；
//结束执行
- (void)speechSynthesizer:(AVSpeechSynthesizer *)synthesizer didFinishSpeechUtterance:(AVSpeechUtterance *)utterance；
//暂停执行
- (void)speechSynthesizer:(AVSpeechSynthesizer *)synthesizer didPauseSpeechUtterance:(AVSpeechUtterance *)utterance；
//继续执行
- (void)speechSynthesizer:(AVSpeechSynthesizer *)synthesizer didContinueSpeechUtterance:(AVSpeechUtterance *)utterance；
//取消时执行
- (void)speechSynthesizer:(AVSpeechSynthesizer *)synthesizer didCancelSpeechUtterance:(AVSpeechUtterance *)utterance；
//朗读某一段执行
- (void)speechSynthesizer:(AVSpeechSynthesizer *)synthesizer willSpeakRangeOfSpeechString:(NSRange)characterRange utterance:(AVSpeechUtterance *)utterance；
demo接口设计与地址
github.com/wxcGit/TTS（demo地址）
