Convert NSString to Integer in objective - c

I have an array that stores each digit of a phone number as a string. I then pass the phone number digit string as an argument for objectAtIndex: method of NSArray like this: [myArray objectAtIndex: [myString intValue]]; The compiler says I need to cast the String but开发者_StackOverflow中文版 I am already doing that. What is wrong?

Update:

Here's my actual line of code:

NSMutableArray *tmp = [[NSMutableArray alloc] initWithArray:[charHolder objectAtIndex:[[phoneNumDigits objectAtIndex:i]intValue]]];

This is where the error is, phoneNumDigits is an array of each digit of the phone number, charHolder is the array holding the array of letters associated with each digit.

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Your question is a little confusing to me. Here is how I understand what you want to do:

You have an NSArray named phoneNumDigits. This array contains a few NSString objects. Each string is something like @"1" or @"4" and represents a single digit of a phone number.

Now you want to convert each of those digit strings to int or NSInteger and want to store these integers in another array.

If I understood you correctly, here is my answer:

You cannot exactly do what you want, because you can't put a simple data type like an int or a float into an NSArray.

That's why there is the wrapper class NSNumber. You can package a simple int in an NSNumber and store this NSNumber in an NSArray.

So to get your string digits from the phoneNumDigits into the tmp array you could use this code:

for (NSString *digitAsString in phoneNumDigits)
{
    NSNumber *digitAsNumber = [NSNumber numberWithInt:[digitAsString intValue]];
    [tmp addObject:digitAsNumber];
}

To get the ints out of the tmp-NSArray you would use

int digit = [[tmp objectAtIndex:idx] intValue];

I hope this helps, but I'm not sure I understand what you want to do here. I could be completely missing the point. Maybe you could share some more code.

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NSMutableArray *tmp = [[NSMutableArray alloc] initWithArray:[charHolder objectAtIndex:[[phoneNumDigits objectAtIndex:i]intValue]]]; 

objectAtIndex returns a generic object (id). It has no idea that the object in the array is a string as it could be anything. So you need to cast it. Or to increase readabilty, create variables for them. Eg:

int phoneNumberDigit = [phoneNumDigits objectAtIndex:i];
NSArray *chars = [charHolder objectAtIndex:phoneNumberDigit];
NSMutableArray *tmp = [[NSMutableArray alloc] initWithArray:chars];