不能继承UIColor？ [英] Can't subclass UIColor?

问题描述

我正在尝试将UIColor子类化，我似乎无法弄清楚出了什么问题。

I'm trying to subclass UIColor, and I can't seem to figure out what's wrong.

在我的PColor.h中

In my PColor.h

#import <Foundation/Foundation.h>
@interface PColor : UIColor {
    BOOL isAvailable;
    int colorId;
}
@property (nonatomic, assign) BOOL isAvailable;
@property (nonatomic, assign) int colorId;
@end

...和我的PColor.m

...and in my PColor.m

#import "PColor.h"

@implementation PColor
@synthesize isAvailable;
@synthesize colorId;
@end

在实例化PColor对象时，我得到：

Upon instantiating a PColor object, I get:

//warning: incompatible Objective-C types initializing 'struct UIColor *', expected 'struct PColor *'
PColor *pcolor = [[PColor alloc] initWithHue:1 saturation:0 brightness:0 alpha:1];

我错过了什么吗？在此先感谢。

Am I missing something? Thanks in advance.

推荐答案

UIColor 是一个类集群使用关联参考在一个类别中添加属性！ UIColor 上的所有自定义init方法都返回 UIColor * 而不是 id 所以你不能轻易地继承 UIColor ，也不应该尝试。

UIColor is a class cluster use associative references in a category to add properties! All of the custom init methods on UIColor return a UIColor* not an id so you can not easily subclass UIColor nor should you try.

UIColor + PCOLOR.h

UIColor+PCOLOR.h

#import <UIKit/UIKit.h>
#import <objc/runtime.h>

@interface UIColor(PCOLOR)
//Properties prefixed to try and avoid future conflicts
@property (nonatomic, assign) BOOL pIsAvailable;
@property (nonatomic, assign) int pColorId;
@end

UIColor + PCOLOR.h

UIColor+PCOLOR.h

#import "UIColor+PCOLOR.h"

@implementation UIColor(PCOLOR)

static char PCOLOR_ISAVAILABLE_KEY;
static char PCOLOR_COLORID_KEY;

@dynamic pIsAvailable, pColorId;

-(void)setPIsAvailable:(BOOL)pIsAvailable
{
    objc_setAssociatedObject(self, &PCOLOR_ISAVAILABLE_KEY, [NSNumber numberWithBool:pIsAvailable], OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}

-(BOOL)pIsAvailable
{
    return [(NSNumber*)objc_getAssociatedObject(self, &PCOLOR_ISAVAILABLE_KEY) boolValue];
}

-(void)setPColorId:(int)pColorId
{
    objc_setAssociatedObject(self, &PCOLOR_COLORID_KEY, [NSNumber numberWithInt:pColorId], OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}

-(int)pColorId
{
    return  [(NSNumber*)objc_getAssociatedObject(self, &PCOLOR_COLORID_KEY) intValue];
}

@end

USAGE

UIColor *pcolor = [[UIColor alloc] initWithHue:1 saturation:0 brightness:0 alpha:1];
pcolor.pColorId = 2352;
pcolor.pIsAvailable = YES;
NSLog(@"\nClass: %@\nColor ID: %d\nIs Availabled: %@", 
      NSStringFromClass([pcolor class]), 
      pcolor.pColorId, 
      pcolor.pIsAvailable ? @"YES" : @"NO");
[pcolor release];

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