xcode4.2中为propery重写setter和getter方法会出现警告：
writable atomic property 'someProperty' cannot pair a synthesized setter/getter with a user defined setter/getter
解决方法之一：在声明propery(nonatomic, ...)中，加入nonatomic
xcode4.2中为propery重写setter和getter方法会出现警告：
writable atomic property 'someProperty' cannot pair a synthesized setter/getter with a user defined setter/getter
解决方法之一：在声明propery(nonatomic, ...)中，加入nonatomic