//這是.h

#import <UIKit/UIKit.h>

NS_ASSUME_NONNULL_BEGIN

@interface UIImage (Category)
@property (nonatomic,strong) UIColor * defaultColor;
@end

NS_ASSUME_NONNULL_END

///這是.m
#import "UIImage+Category.h"
#import <objc/runtime.h>


@implementation UIImage (Category)

static char kDefaultColorKey;

@dynamic defaultColor;


- (void) setDefaultColor:(UIColor *)defaultColor {
    objc_setAssociatedObject(self, &kDefaultColorKey, defaultColor, OBJC_ASSOCIATION_COPY_NONATOMIC);
}

- (UIColor *)defaultColor {
    return objc_getAssociatedObject(self, &kDefaultColorKey);
}

@end

如代碼所示:先用objc_setAssociatedObject 給UIImage關(guān)聯(lián)一個UIColord的屬性defaultColor
用的時候用objc_getAssociatedObject讀取關(guān)聯(lián)的UIColor的屬性。

• 注意：在設置屬性的時候用@dynamic來告訴編譯器不要自動生成get和set方法
  使用的時候如下:

UIImage * img =[UIImage imageNamed:@"login_icon1"];
Class cla = [UIImage class];
    
imageView.image = img;
img.defaultColor = UIColor.redColor; 
NSLog(@"%@",img.defaultColor);