成员变量应该是 @private

Tip 成员变量应该声明为 @private 1. @interface MyClass : NSObject { 2. @private 3. id myInstanceVariable_; 4. } 5. // public accessors, setter takes ownership 6. - (id)myInstanceVariable; 7. - (void)setMyInstanceVariable:(id)theVar; 8. @end