Integer Casting in dealing with strings in Cocoa

Question

I have what I hope to be a pretty simple problem. I'm very simply trying to convert a char to it's lowercase version. Here's my code:

- (IBAction)click:(id)sender { 
    [outputLabel setText:[inputField text]];
    NSString* textFieldString = [inputField text];
    NSLog(@"String is %@", textFieldString);
    int textFieldLength = textFieldString.length;
    UniChar* currChar = [textFieldString characterAtIndex:0];
    NSLog(@"First char is %c", currChar);
    NSLog(@"Length is %i", textFieldLength);
    //currChar = [currChar lowercaseString];
    //NSLog(@"Lowercase char is %c", currChar);
}

It's giving me a the following error:

Initialization makes pointer from integer without a cast on the line:
NSString* currChar = [textFieldString characterAtIndex:0];

However, when looking in the documentation, it says that the method characterAtIndex: returns a char, not an integer. What gives?

Answer 1

This is the definition for that function:

- (unichar)characterAtIndex:(NSUInteger)index

A unichar is a c data type, and is not a NSString *. You need to do

unichar currChar = [textFieldString characterAtIndex:0];

The message you're getting is due to it trying to cast the integer value of the unichar to a pointer value.

EDIT:

BTW, if you really need a NSString back from that the easiest way would probably be (dry-code):

NSString *currChar = [textFieldString substringWithRange:NSMakeRange(0,1)];

Answer 2

characterAtIndex returns unichar which is an unsigned short. The line should be

unichar currChar = [textFieldString characterATtIndex:0];

Also, you can just use lowercaseString to get the lowercase of the entire NSString:

NSString *lowercase = [textFieldString lowercaseString];