Objective C Boolean Array

问题:

I need to utilize an array of booleans in objective-c. I've got it mostly set up, but the compiler throws a warning at the following statement:

[updated_users replaceObjectAtIndex:index withObject:YES];

This is, I'm sure, because YES is simply not an object; it's a primitive. Regardless, I need to do this, and would greatly appreciate advice on how to accomplish it.

Thanks.

回答1:

Yep, that's exactly what it is: the NS* containers can only store objective-C objects, not primitive types.

You should be able to accomplish what you want by wrapping it up in an NSNumber:

[updated_users replaceObjectAtIndex:index withObject:[NSNumber numberWithBool:YES]]

or by using @(YES) which wraps a BOOL in an NSNumber

[updated_users replaceObjectAtIndex:index withObject:@(YES)]]

You can then pull out the boolValue:

BOOL mine = [[updated_users objectAtIndex:index] boolValue];

回答2:

Assuming your array contains valid objects (and is not a c-style array):

#define kNSTrue         ((id) kCFBooleanTrue)
#define kNSFalse        ((id) kCFBooleanFalse)
#define NSBool(x)       ((x) ? kNSTrue : kNSFalse)

[updated_users replaceObjectAtIndex:index withObject:NSBool(YES)];

回答3:

You can either store NSNumbers:

[updated_users replaceObjectAtIndex:index
                         withObject:[NSNumber numberWithBool:YES]];

or use a C-array, depending on your needs:

BOOL array[100];
array[31] = YES;

回答4:

Like Georg said, use a C-array.

BOOL myArray[10];

for (int i = 0; i < 10; i++){
  myArray[i] = NO;
}

if (myArray[2]){
   //do things;
}

Martijn, "myArray" is the name you use, "array" in georg's example.

回答5:

From XCode 4.4 you can use Objective-C literals.

[updated_users replaceObjectAtIndex:index withObject:@YES];

Where @YES is equivalent of [NSNumber numberWithBool:YES]

回答6:

If your collection is large or you want it to be faster than objc objects, try the CFBitVector/CFMutableBitVector types found in CoreFoundation. It's one of the CF-Collections types which does not ship with a NS counterpart, but it can be wrapped in an objc class quickly, if desired.