参考：YYKit 核心**，非YYKit实现
demo 仅供参考
http://code.cocoachina.com/view/1000646
To run the example project, clone the repo, and run pod install from the Example directory first.
DDCoreTextLabel is available through CocoaPods. To install it, simply add the following line to your Podfile:
pod 'DDCoreTextLabel'liuhedong01@163.com, liuhedong01@163.com
DDCoreTextLabel is available under the MIT license. See the LICENSE file for more info.