Objective-C NSString for loop with characterAtIndex

Question

I\'m trying to loop through a NSString, character by character, but I\'m getting a EXC_BAD_ACCESS error. Do you have an idea how to do this right? I\'ve been googling for hours

Answer 1

characterAtIndex: returns a unichar, so you should use NSLog(@"%C", ...) instead of @"%@".

You also cannot use isEqualToString for a unichar, just use == '.' is fine.

If you want to find the position of all '.'s, you can use rangeOfString. Refer to:

• String Programming Guide: Searching, Comparing, and Sorting Strings
• Position of a character in a NSString or NSMutableString

Answer 2

characterAtIndex: returns a unichar, which is declared as typedef unsigned short unichar; The format specifier you are using in your calls to NSLog are incorrect, you could just do NSLog(@"%u",[self.text characterAtIndex:position]); or NSLog(@"%C",[self.text characterAtIndex:position]); if you want the actual character to print out.

Also, as a result of unichar being defined the way that it is, it's not a string, so you cannot compare it to other strings. Try something like:

unichar textCharacter = '.';

if ([self.text characterAtPosition:position] == testCharacter) {
   // do stuff
}

Answer 3

If you want to find the location of a character in a string you can use this:

NSUInteger position = [text rangeOfString:@"."].location;

if the character or text is not found you will get a NSNotFound:

if(position==NSNotFound)
    NSLog(@"text not found!");

Answer 4

Characters are not object. characterAtIndex returns unichar, which is actually an integer type unsigned short. You need to use %C instead of %@ in NSLog. Also character is not a NSString, so you can't send it isEqualToString. You need to use ch == '.' to compare ch against '.'.

unichar ch = [self.text characterAtIndex:position];
NSLog(@"%C", ch);

if (ch == '.') {} // single quotes around dot, not double quotes

Note that, 'a' is character, "a" is C string and @"a" is NSString. They all are different types.

When you are using %@ with unichar ch in NSLog, it is trying to print an object from memory location ch which is invalid. Thus you are getting a EXC_BAD_ACCESS.