CODEWITHSUNDEEP
iphoneobjective-cnsarray
Mat
Mat

Reputation: 6324

NSArray - objectAtIndex:

I have a problem. I get an error if the objectAtIndex:x is empty. In my code the user has to insert a code separated by "/" like 32/31/43 or even 32//12. Everything works but if the user insert a single number without the "/" I got the error shown in the picture but I would like to get an alert view that tell the user that the code has been inserted in a wrong format. I hope it's clear. thanks enter image description here

Upvotes: 1

Views: 3185

Answers (3)

kball
kball

Reputation: 4971

For the string "2" componentsSeparatedByString will return an array with only a single object: the string "2".

You are trying to read an object at index 1 (ie the second object), but the array only has one object. It is an error to try to read a value from beyond the end of an NSArray.

It seems like what you're trying to do is require that the value entered has two '/'s so why not check that first?

if ([componentDepthString count] != 3) {
   // show an alert and return
}

Upvotes: 0

Seamus Campbell
Seamus Campbell

Reputation: 17906

You can test the number of components in the array with

[componentDepthString count]

Before you go blindly poking into the array, make sure the array has as many elements as you need it to:

// probably a bad idea to name the array with the word "string in it
NSArray *componentDepths = [depthString componentsSeparatedByString:@"/"];
NSInteger numComponents = [componentDepths count];

if(numComponents < 3) {
    // show an alert...

    return;
}

// otherwise proceed as before

Upvotes: 2

justin
justin

Reputation: 5831

Probably the best way to go about it is to check your array after you created it to make sure there are 3 values.

NSArray *componentDepthString = [depthString componentsSeperatedByString:@"/"];
if ([componentDepthString count] == 3) {
    // everything is good and you can continue with your code;
    //  rest of the code;
} else {
    // the user input bad values or not enough values;
    UIAlertView *myAlert = [[UIAlertView alloc] 
                                    initWithTitle:@"can't continue"
                                    message:@"user input bad values"
                                    delegate:self
                                    cancelButtonTitle:@"Cancel"
                                    otherButtonTitles:nil];
    [myAlert show];
    [myAlert release];
}

EDIT: you will have to edit the title and message to say what you want, but that's the basic idea on how to check for bad data before the error and how to display a warning. You will have to add your own logic how to handle it with the user

Upvotes: 2

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