Using NSDictionary instead of NSArray

Question

Hi, 
I've tried to create NSDictionary instead of NSArray to store different colors for my app. I also create a method with UIColor return type (just like Pasan did) and one parameter of type NSString but without using arc4random. 
(instancetype)init
{
self = [super init];
if (self) {
    _kolory = [[NSDictionary alloc]initWithObjectsAndKeys:
               @[[UIColor colorWithRed:222/255.0 green:171/255.0 blue:66/255.0 alpha:1.0]], @"Tło",
               @[[UIColor colorWithRed:85/255.0 green:176/255.0 blue:112/255.0 alpha:1.0]], @"Wygrana",
               @[[UIColor colorWithRed:223/255.0 green:171/255.0 blue:66/255.0 alpha:1.0]], @"Przegrana", nil];
}
return self;
}
(UIColor *)wyborKoloruDlaElementu: (NSString *)element {
return [self.kolory objectForKey:element]; 
}
My goal is to change background color by calling a method with an argument of type NSString that match a key in my NSDictionary. 
self.view.backgroundColor = [self.koloryElementow wyborKoloruDlaElementu:@"Tło"];
When i try to run the app with calling the method - return UIApplicationMain(argh, argue, nil, NSStringFromClass([AppDelegate class])); Thread1: signal SIGABRT
Where is the problem?
Thanks in advance for your help!

John W · Accepted Answer

Let's examine the objects you inserted into your dictionary:
@"Tło": @[[UIColor colorWithRed:222/255.0 green:171/255.0 blue:66/255.0 alpha:1.0]]
For the values of your dictionary,  [UIColor colorWithRed:green:blue:alpha:] creates a UIColor object, while wrapping that into @[ .... ] actually creates an NSArray that contains that object.
So when you try to retrieve that object later with [self.kolory objectForKey:element] (or with a more modern syntax: self.kolory[element]), you actually obtained an NSArray contain a single UIColor instead of just a UIColor. From there you probably sent that object (again, NSArray containing a UIColor) to something that was expecting just a UIColor.

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Jacek Gałka

Jacek Gałka

Using NSDictionary instead of NSArray

1 Answer

John W

John W

Jacek Gałka

Jacek Gałka