Question

How can I tell UITextView to set the cursor to a particular line (line 13, for example) when it appears?

Answer 1

UITextView has a method setSelectedRange: (NSRange) range.

If you know where in the string line 13 occurs, say location 237, then do: [textView setSelectedRange: NSMakeRange(237,0)];

If you need to find out where line 13 occurs, you’ve more work ahead. I’d start by looking at sizeWithFont, remembering to nip about 16 points off the width of your textView so that iOS gets the sums right. (That said, if you have line breaks, then just find the location of the 13th (or nth) “\n”.)

Update following your further query in the comment

There are lots of ways of finding the position of the nth \n. The following snippet isn’t pretty, but it will do the job. You could also use rangeOfString and iterate through the “\n”. In this snippet, if the target line is greater than the number of lines, it puts the cursor at the end. The code here assumes you have a UITextView property called userEntry.

int targetLine = 3; // change this as appropriate 0=first line

NSRange range;

NSString* exampleString = @"Hello there\nHow is it going?\nAre you looking for a new line?\nA new line in what?\nThat remains to be seen";

NSArray* separateLines = [exampleString componentsSeparatedByString:@"\n"];

if (targetLine < [separateLines count])
{
    int count = 0;
    for (int i=0; i<targetLine; i++)
    {
        count = count + [[separateLines objectAtIndex:i] length] + 1; // add 1 to compensate \n separator
    }

    range = NSMakeRange(count, 0);
}
else
{
    range = NSMakeRange([exampleString length], 0); // set to the very end if targetLine is > number of lines
}

[[self userEntry] setText: exampleString];
[[self userEntry] setSelectedRange:range];
[[self userEntry] becomeFirstResponder];