Check if a BOOL is set (can't be done with ==nil)

how do i check if a BOOL is set in objective-c (iphone)?

i know that it can be done with an int or float this way: NSNumber *Num = [prefs floatForKey:@"key"开发者_JAVA技巧]; for example

You can't. A BOOL is either YES or NO. There is no other state. The way around this would be to use an NSNumber ([NSNumber numberWithBool:YES];), and then check to see if the NSNumber itself is nil. Or have a second BOOL to indicate if you've altered the value of the first.

Annoyingly, Objective-C has no Boolean class. It certainly feels like it should and that trips a lot of people up. In collections and core data, all bools are stored as NSNumber instances.

It's really annoying having to convert back and forth all the time.

By default, a bool value is set to 0 in Objective-C, so you don't need to check if your bool value is nil anytime.

You can use something like this instead...

@import Foundation;

@interface CSBool : NSObject

+ (CSBool *)construct:(BOOL)value;

@property BOOL value;

@end

#import "CSBool.h"

@implementation CSBool

+ (CSBool *)construct:(BOOL)value {
    CSBool *this = [self new];
    this.value = value;
    return this;
}
@end