CODEWITHSUNDEEP
iosobjective-cobjective-c-category
Apollo
Apollo

Reputation: 9062

Category that returns array of uicolors

I have the following category extension of UIColor:

.h

#import <UIKit/UIKit.h>

@interface UIColor (Colors)
- (NSArray *)reds;
@end

.m

#import "UIColor+Colors.h"

@implementation UIColor (Colors)

- (NSArray *)reds {
    return [[NSArray alloc] initWithObjects:[UIColor colorWithRed:1.0/255.0 green:50.0/255.0 blue:98.0/255.0 alpha:1],[UIColor colorWithRed:1.0/255.0f green:37.0f/255.0f blue:75.0f/255.0f alpha:1],[UIColor colorWithRed:1.0/255.0 green:1.0/255.0 blue:52.0/255.0 alpha:1],[UIColor colorWithRed:90.0/255.0 green:13.0/255.0 blue:1.0/255.0 alpha:1],[UIColor colorWithRed:53.0/255.0 green:6.0/255.0 blue:1.0/255.0 alpha:1], nil];
}

@end

Then in a viewcontroller, I'm trying to do something like this: [cell setBackgroundColor:[UIColor reds][0]]; Any idea what I'm doing wrong?

Upvotes: 1

Views: 200

Answers (2)

Duncan C
Duncan C

Reputation: 131436

As the others have pointed out, you want to create a class method (method who's definition starts with "+") not an instance method.

However, your code is pretty pointless, since you create and return a new array of UIColor objects every time the class method is called.

That's your only real option in a category since categories can't add instance variables or global variables. You might be able to use associative storage, but I'm not sure how you'd use associative storage from a class method.

Upvotes: 1

Ron
Ron

Reputation: 1269

I think the most likely problem is that the function reds needs to be a class method for you to be able to call reds on the class. So something like this:

.h

@interface UIColor (Colors)
   +(NSArray *)reds;
@end

.m

@implementation UIColor (Colors)

+(NSArray *)reds {
    return @[[UIColor colorWithRed:1.0/255.0 green:50.0/255.0 blue:98.0/255.0 alpha:1],
             [UIColor colorWithRed:1.0/255.0f green:37.0f/255.0f blue:75.0f/255.0f alpha:1],
             [UIColor colorWithRed:1.0/255.0 green:1.0/255.0 blue:52.0/255.0 alpha:1],
             [UIColor colorWithRed:90.0/255.0 green:13.0/255.0 blue:1.0/255.0 alpha:1],
             [UIColor colorWithRed:53.0/255.0 green:6.0/255.0 blue:1.0/255.0 alpha:1]];
}

@end

So basically a + instead of a -. If you use - it is an instance method so you'd have to instantiate an instance of UIColor to call reds.

Upvotes: 6

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