oc是运行时才寻找方法，有可能在运行的时候找不到类，可以关注下这里是否加入.m文件

Key-value codingis a mechanism for accessing an object’s properties indirectly, using strings to identify properties, rather than through invocation of an accessor method or accessing them directly

The Cocoa (Application) layer includes the frameworks described in the following sections. Cocoa in the architecture of OS X Cocoa Umbrella Framework The Cocoa umbrella framework (Cocoa

UIView: The UIView class defines a rectangular area on the screen and the interfaces for managing the content in that area. At runtime, a view object handles the rendering of any content in its are

http://ke.indiebros.com/2012/08/20/ios-app-performance-strategy/ 性能问题的处理流程 发现/重现问题利用工具剖析形成假设改进代码和设计 在以上的四个步骤中循环反复，直到问题解决。 Profile!不要猜! 性能优化的主要策略： 不要做无用功：不要在启动时花几百ms来做logg

http://blog.sina.com.cn/s/blog_6f40a0e70100srix.html  1.创建NSConnection对象，设置委托对象          NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:[self urlStrin

The observing class must implement observeValueForKeyPath:ofObject:change:context:. Registering as an Observer In order to be notified of changes to a property, an observing object must firs