readonly & readwrite

配合使用，一般在.h文件中如下定义

@interface XXXXX
@property (readonly, nonatomic, assign) int age;
@end

而在.m中：

@interface XXXXX()
@property (readwrite, nonatomic, assign) int age;
@end
@implementation XXXXX
@end

这样就可以在.m中使用
self.age = 1;
这样的语句了。

类属性

关键词: class
.h文件中

@interface RXAFNTest3Object : NSObject
@property (nonatomic, assign, class) NSInteger value;
@end

.m文件中

static NSInteger s_Value = 0;
@implementation RXAFNTest3Object
+ (NSInteger)value {
    return s_Value;
}
+ (void)setValue:(NSInteger)value {
    s_Value = value;
}
@end

在分类中添加属性

@interface UIViewController (Mediator)
@property (nonatomic, copy) NSString *rx_string; 
@end

- (NSString *)rx_string {
    return objc_getAssociatedObject(self, @"rx_string");
}
- (void)setRx_string:(NSString *)rx_string {
    objc_setAssociatedObject(self, @"rx_string", rx_string, OBJC_ASSOCIATION_COPY);
}

在分类中添加weak属性

http://mrpeak.cn/blog/ios-weak/

- (void)setContext:(CDDContext*)object {
    id __weak weakObject = object;
    id (^block)() = ^{ return weakObject; };
    objc_setAssociatedObject(self, @selector(context), block, OBJC_ASSOCIATION_COPY);
}

- (CDDContext*)context {
    id (^block)() = objc_getAssociatedObject(self, @selector(context));
    id curContext = (block ? block() : nil);
    return curContext;
}

TODOAFN_M_2_K_5