Objective-C is an amazing skill -- used to add macros to attributes in category, and objective-c

Objective-C is an amazing skill -- used to add macros to attributes in category, and objective-c

Technical lust refers to technologies and products that are too clever and useless.
Reprinted please indicate the source http://blog.csdn.net/uxyheaven/article/details/46789065

As we all know, in general, we cannot add attributes to category.
Associated is required if you want to add it.

@interface NSObject (XYFlyweightTransmit)@property (nonatomic, strong) id uxy_flyweightData;@end@implementation NSObject (UXYFlyweightTransmit)- (id)uxy_flyweightData{    return objc_getAssociatedObject(self, NSObject_key_flyweightData);}- (void)setUxy_flyweightData:(id)flyweightData{    objc_setAssociatedObject(self, NSObject_key_flyweightData, flyweightData, OBJC_ASSOCIATION_RETAIN_NONATOMIC);}@end;

If you need to write so much code each time to implement it, it is really complicated.
Generally, we encapsulate the following code:

@interface NSObject (XY_associated)- (id)uxy_getAssociatedObjectForKey:(const char *)key;- (id)uxy_retainAssociatedObject:(id)obj forKey:(const char *)key;- @end@implementation NSObject (XY_associated)- (id)uxy_getAssociatedObjectForKey:(const char *)key{    const char * propName = key;    id currValue = objc_getAssociatedObject( self, propName );    return currValue;}- (id)uxy_retainAssociatedObject:(id)obj forKey:(const char *)key;{    const char * propName = key;    id oldValue = objc_getAssociatedObject( self, propName );    objc_setAssociatedObject( self, propName, obj, OBJC_ASSOCIATION_RETAIN_NONATOMIC );    return oldValue;}

In this way, we only need to add an attribute as follows:

- (UIView *)overlay{    return [self uxy_getAssociatedObjectForKey:"xy.navigationBar.overlay"];}- (void)setOverlay:(UIView *)overlay{    [self uxy_retainAssociatedObject:overlay forKey:"xy.navigationBar.overlay"];}

The above Code seems to be a lot of repetitive. We are using a macro to encapsulate it.
However, when we really write macros, we find that the get method is easy to write, and the set Method is useless, because it is followed by an uppercase letter.
The following solution is generally used:
* The agreed attribute must start with an uppercase letter.
* Starting with an underscore
* When writing a macro, pass in the setName name.

However, the title of this article is not the above method.
Let's take a look at what the code looks like.

@interface UINavigationBar (XY)uxy_property_as_associated_strong(id, test2);@end@implementation UINavigationBar (XY)uxy_property_def_associated_strong(id, test2)@end{    self.test2 = @"a";    id c = self.test2;    NSLog(@"%@", c);}

Implementation ideas:
When declaring an attribute, use setter to modify the set Method of the attribute, and add _ in front to avoid case sensitivity.

The specific implementation code is as follows:

#define uxy_property_as_associated_strong( __type, __name) \        @property (nonatomic, strong, setter=set__##__name:, getter=__##__name) __type __name;#define uxy_property_def_associated_strong( __type, __name) \        - (__type)__##__name   \        { return [self uxy_getAssociatedObjectForKey:#__name]; }   \        - (void)set__##__name:(id)__##__name   \        { [self uxy_retainAssociatedObject:__##__name forKey:#__name]; }

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