category

category使用 objc_setAssociatedObject/objc_getAssociatedObject 实现添加属性

属性 其实就是get/set 方法。我们可以使用  objc_setAssociatedObject/objc_getAssociatedObject  实现 动态向类中添加 方法

@interface NSObject (CategoryWithProperty)

@property (nonatomic, strong) NSObject *property;

@end

@implementation NSObject (CategoryWithProperty)

- (NSObject *)property {
return objc_getAssociatedObject(self, @selector(property));
}

- (void)setProperty:(NSObject *)value {
objc_setAssociatedObject(self, @selector(property), value, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}

@end

objective-c中，有类别可以在不修改源码的基础上增加方法；近排在看别人的开源代码时，发现还可以动态增加属性。而且是在运行时,太牛B了。

使用运行时库，必须要先引入 objc/runtime.h

可以使用的函数如下：

OBJC_EXPORT void objc_setAssociatedObject(id object, const void *key, id value, objc_AssociationPolicy policy)

这个函数

OBJC_EXPORT id objc_getAssociatedObject(id object, const void *key)
__OSX_AVAILABLE_STARTING(__MAC_10_6, __IPHONE_3_1);

 

兄弟们，看一个类别和动态添加属性的例子：

UILabel+Associate.h

#import <UIKit/UIKit.h>

@interface UILabel (Associate)

- (void) setFlashColor:(UIColor *) flashColor;

- (UIColor *) getFlashColor;

@end

UILabel+Associate.m

#import "UILabel+Associate.h"
#import <objc/runtime.h>

@implementation UILabel (Associate)

static char flashColorKey;

- (void) setFlashColor:(UIColor *) flashColor{
objc_setAssociatedObject(self, &flashColorKey, flashColor, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}

- (UIColor *) getFlashColor{
return objc_getAssociatedObject(self, &flashColorKey);
}

@end

调用代码：

UILabel *lab = [[UILabel alloc] init];
[lab setFlashColor:[UIColor redColor]];
NSLog(@"%@", [lab getFlashColor]);

//

//  UIAlertView+ShowWithBlock.h

#import <UIKit/UIKit.h>

typedef void (^alertBlock)(UIAlertView *alertView,
NSInteger buttonIndex);

@interface UIAlertView (UIAlertView_Category)<UIAlertViewDelegate>

-(void)showWithBlock:(alertBlock)block;

@end

//  UIAlertView+ShowWithBlock.m

#import "UIAlertView+Category.h"

#import <objc/runtime.h>

static NSString *MyAlertAction =
@"MyAlertAction";

@implementation UIAlertView (UIAlertView_Category)

- (void)showWithBlock:(alertBlock)block

{

    if (block){

        objc_removeAssociatedObjects(self);

        objc_setAssociatedObject(self, (__bridge
const
void *)(MyAlertAction), block,
OBJC_ASSOCIATION_RETAIN_NONATOMIC);

        self.delegate =
self;

    }

    [self
show];

}

- (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex

{

    alertBlock block =
objc_getAssociatedObject(self, (__bridge
const void *)(MyAlertAction));

    block(alertView, buttonIndex);

}

@end