Perform same action for many objects

Question

If I have 100 UITextFields,

myTextfFeld1, myTextField2...and so on until mytextField100

...and they all perform the same action, say change myTextField1.alpha = 0.4 to myTextField1.alpha = 1.

Rather than write this out 100 times is there a more efficient way of doing this

I had a look here iOS looping over an object's properties and adding actions but it still means adding all the UITextFields into the array.

Having 100 ivars is silly. Use an NSArray or IBOutletCollection. — rmaddy, Jun 23 '13 at 18:22
I haven't got 100 ivars, just an exaggeration during my explanation of what I was tying to put across in my question. Agreed with both comments — JSA986, Jun 23 '13 at 18:35

score 6 · Accepted Answer · answered Jun 23 '13 at 18:23

6

Please, no!

Like this.

Use an array, seriously. Don't you dare having 100 instance variables named textField1 to textField100!

Just in order to actually answer your question: you still can do this. Again, I strongly discourage doing it, but just for completeness' sake, here's the code:

for (int i = 1; i <= 100; i++) {
    NSString *ivarName = [NSString stringWithFormat:@"myTextField%d", i];
    UITextField *tf = [self valueForKey:ivarName];
    [tf doWhateverYouWant];
}

Reflection in Objective-C is awesome, isn't it? Not quite when abused.

answered Jun 23 '13 at 18:23

I would dream of it its just example text for SO – JSA986 Jun 23 '13 at 18:26
@JSA986 Sorry, I don't understand what you mean, please elaborate. – Jun 23 '13 at 18:27
I wouldn't actually have a 100 instance variables named `myText1`etc. They were hypothetical instance variable for simplicity when posting my question. They have much better naming conventions than that ;-) Thanks for answer thats exactly was after! – JSA986 Jun 23 '13 at 18:30

score 1 · Answer 2 · answered Jun 23 '13 at 18:23

1

You can define an outlet collection and connect all of the textfields to it from the XIB:

 @property (nonatomic, weak) IBOutletCollection(UITextField) NSArray *textFields;

Then you can loop over the textFields array.

answered Jun 23 '13 at 18:23

Wain

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...or instead of looping, you can use the method `–makeObjectsPerformSelector:withObject:` on the `NSArray`. – holex Jun 23 '13 at 18:36
1

@holex, true, assuming that the method takes an object parameter (so couldn't be used for setting the `alpha` for example) – Wain Jun 23 '13 at 18:37
yep, you are absolutely right, it needs a little play with the `NSInvocation` for the non-object parameters. it depends on the code-pattern the poster has chosen, but that was not part of the original question, I think. – holex Jun 23 '13 at 19:06

score -2 · Answer 3 · answered Jun 23 '13 at 18:24

-2

Use a loop and an array for the textfields. e.g.

int i = 0
do textfield[i].alpha = 1
i = i+1
until i = 100

answered Jun 23 '13 at 18:24

user2369405

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The question is tagged Objective-C. Answers should be in the same language. – rmaddy Jun 23 '13 at 18:38
Are you allowed? Sure. But to be helpful, your answer should provide usable code appropriate to the question. – rmaddy Jun 24 '13 at 04:34

Perform same action for many objects

3 Answers3