How to convert and compare NSNumber to BOOL?

Question

First I convert BOOL value to NSNumber in order to put it into NSUserDefaults. Later I would like to retrieve the BOOL value from the NSUserDefaults, but obviously I get NSN

Answer 1

The ONLY way I managed to finagle a NSNumber's "booleanity" from its NSConcreteValue(doh!) was with the following...

id x = [self valueForKey:@"aBoolMaybe"];
if ([x respondsToSelector:@selector(boolValue)] && 
    [x isKindOfClass:objc_getClass("__NSCFNumber")])
    [self doSomethingThatExpectsABool:[x boolValue]];

Every other trick... FAILED. Buyer beware, this isn't foolproof (__NSCFNumber may well be platform/machine specific - it is solely Apple's implementation detail)... but as they say.. nothing else worked!

Answer 2

Swift 4:

let newBoolValue = nsNumberValue.boolValue

Answer 3

NSUserDefaults has two methods to transparently operate with booleans:

- (BOOL)boolForKey:(NSString *)defaultName

- (void)setBool:(BOOL)value forKey:(NSString *)defaultName

Answer 4

You currently compare two pointers. Use NSNumbers methods instead to actually compare the two:

if([someNSNumberValue isEqualToNumber:[NSNumber numberWithBool:NO]]) {
    // ...
}

To get the bool value from a NSNumber use -(BOOL)boolValue:

BOOL b = [num boolValue];

With that the comparison would be easier to read for me this way:

if([num boolValue] == NO) {
    // ...
}