Set bool property of all objects in the array

Question

I've a model class called PhotoItem. In which I have a BOOL property isSelected

@interface PhotoItem : NSObject

/*!
 * Indicates whether the photo is selected or not
 */
@property (nonatomic, assign) BOOL isSelected;

@end

I've an NSMutableArray which holds the object of this particular model. What I want to do is, in a particular event I want to set the bool value of all objects in the array to true or false. I can do that by iterating over the array and set the value.

Instead of that I tried using:

[_photoItemArray makeObjectsPerformSelector:@selector(setIsSelected:) withObject:[NSNumber numberWithBool:true]];

But I know it won't work and it didn't. Also I can't pass true or false as the param in that (since those are not object type). So for fixing this issue, I implemented a custom public method like:

/*!
 * Used for setting the photo selection status
 * @param selection : Indicates the selection status
 */
- (void)setItemSelection:(NSNumber *)selection
{
    _isSelected = [selection boolValue];
}

And calling it like:

[_photoItemArray makeObjectsPerformSelector:@selector(setItemSelection:) withObject:[NSNumber numberWithBool:true]];

It worked perfectly. But my question is, Is there any better way to achieve this without implementing a custom public method ?

Sidenote: The isSelected name for the property seems a bit odd. Apple uses a scheme where boolean properties are named with a simple adjective and have a setter name that uses the "is" prefix, like @property (getter=isSelected) BOOL selected;. This is even documented in the KVC guide explaining how keys are resolved. — Nikolai Ruhe
– Nikolai Ruhe, Commented Oct 8, 2015 at 11:55

Nikolai Ruhe · Accepted Answer · 2015-10-08 12:26:21Z

8

Is there any better way to achieve this without implementing a custom public method?

This sounds like you are asking for opinion, so here is mine: Keep it simple.

for (PhotoItem *item in _photoItemArray)
    item.isSelected = YES;

Why obfuscate a simple thing with detours through obscure methods when you can write code that anybody will immediately understand?

Another way of doing the same thing would be:

[_photoItemArray setValue:@YES forKey:@"isSelected"];

This does not need the custom additional setter method because KVC does the unboxing for you.

But again I would vote against using such constructs. I think they are distracting from the simple meaning and confusing developers that come after you.

edited Oct 8, 2015 at 12:26

answered Oct 8, 2015 at 11:48

Nikolai Ruhe

81.9k17 gold badges184 silver badges202 bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

Rob Napier Over a year ago

+1 Worth emphasizing the use of YES here, which is not the same as true, and is one of the mistakes in the original code. (But agreed, a for loop is best.)

Duncan C Over a year ago

Using KVC seems about as clear as the for loop method to me, once you know that KVC methods on arrays forward the action to every item in the array. Learning this seems to me a bit like getting used to the trinary (?:)operator. It seems odd the first few times you encounter it, and then becomes natural. KVC does have some overhead, so the for..in loop is probably a little more performant, but the difference will be undetectable for all but the largest arrays.

Midhun MP Over a year ago

@RobNapier: I didn't understand your comment. Can you please elaborate ? What is the mistake in original code with the use of true ? In my understanding both YES and true serve the same purpose (correct me if I'm wrong)

Rob Napier Over a year ago

"Same purpose" sure in that they are both "true-like things." But they're different types. You can't substitute one for the other in general (and the bugs it can cause are truly glorious; I've had wonderful variables that were true, not-true, false, or not-false depending on how you tested them). In the majority of cases when dealing with ObjC, you want YES. It is very rare to use true (which is only in the language because it was inherited from recent updates to C).

Collectives™ on Stack Overflow

Set bool property of all objects in the array

1 Answer 1

4 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

4 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related