UITextView word wrapping with maximum line-length and lines - ios

Question

For an iOS application I am writing I am using an UITextView, where the user can insert a limited text.
To the textview there are 2 restrictions:
Lines can be no longer than 30 characters
There can be only 20 lines of text in the UITextView.
So in short, the maximum is 20 lines of 30 characters.
When a user is typing some text in the UITextView and the current sentence is 30 characters, I want it to automatically insert a new line \n (before the last word on that line) and force the last word and cursor to the line below.
When a user has 20 lines with 30 characters (or even simpler said: 20 lines, with 30 characters on the last line) I want the input to be blocked.
Now, most of this is fairly 'simple' but the code I have does not account for border cases, like inserting text in earlier lines.
I looked around the documentation from Apple, but I can not find a way to actually force this kind of Word-wrapping on a UITextView.
My try is to handle all this in the shouldChangeTextInRange delegate method (made the code a little more verbose, so it's a bit easier to read).
#define MAX_LENGTH_LINE 30
#define MAX_LENGTH_ROWS 20
- (BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)text
{
// Check for backspaces, they should always be allowed?
if ([text length] == 0 && ![text isEqualToString:#"\n"])
return YES;
NSArray* lines = [textView.text componentsSeparatedByString:#"\n"];
// Check if there are a maximum of lines and the last line is already maxed out
NSString* lastLine = [lines objectAtIndex:[lines count] - 1];
if (([lines count] == MAX_LENGTH_ROWS) &&
(lastLine != nil) &&
([lastLine length] > MAX_LENGTH_LINE) &&
([text length] > 0))
return NO;
if ((lastLine != nil) &&
([lastLine length] > MAX_LENGTH_LINE))
{
NSRange range = [textView.text rangeOfString:#" " options:NSBackwardsSearch];
NSRange breakRange = [textView.text rangeOfString:#"\n" options:NSBackwardsSearch];
if (breakRange.location == NSNotFound)
breakRange = NSMakeRange(0, 1);
if (range.location == NSNotFound) {
range = NSMakeRange(0, 1);
}
if (range.location > breakRange.location)
{
textView.text = [textView.text stringByReplacingCharactersInRange:NSMakeRange(range.location, 1) withString:#"\n"];
}
else
{
textView.text = [textView.text stringByAppendingString:#"\n"];
}
}
if ([text isEqualToString:#"\n"])
{
if ([lines count] == MAX_LENGTH_ROWS)
return NO;
else {
return YES;
}
NSRange range = NSMakeRange(textView.text.length - 1, 1);
[textView scrollRangeToVisible:range];
}
return YES;
}
In the meanwhile I have been at this for a while and I lost it at the moment. Anyone who can give some pointers to just limit the UITextView to the 20 lines / 30 characters limitation I want?

Answer 1

This may be counter to your overall goals, but the simplest answer in my head is to reparse the string every time the user adds a character. Then it wouldn't matter where the character was added. Instead of doing all this in shouldChangeTextInRange: do it in textViewDidChange:. You will need to be a UITextViewDelegate and you will need a single class NSString to hold the last successful user text update in case your user is trying to add a character beyond the allowed limit.
Something like this:
-(void)textViewDidChange:(UITextView *)textView
{
//Get the textview without any new line characters
NSMutableString *temporaryString = [NSMutableString stringWithString:[textView.text stringByReplacingOccurrencesOfString:#"\n" withString:#" "]];
bool updatePossible = true;
int i = 0, numberOfLinesSoFar = 0;
while(i + 30 < [temporaryString length])
{
//Go 30 characters in and start the reverse search for a word separation
i += 30;
int j = i;
//Get the location of the final word separation in the current line
while(j >= i && [temporaryString characterAtIndex:j] != ' ')
{
j--;
}
//This means we found a word separation
if(j > i)
{
i = j;
[temporaryString replaceCharactersInRange:NSMakeRange(i,1) withString:#"\n"];
}
//We didn't find a word separation
else
{
//Here we will just have to break the line at 30.
[temporaryString insertString:#"\n" atIndex:i];
}
numberOfLinesSoFar++;
//Check if we just wrote line 20 and still have characters to go.
if(numberOfLinesSoFar > 19 && i < [temporaryString length])
{
//Revert user change to the last successful character addition
textView.text = lastSuccessfulViewString;
updatePossible = false;
break;
}
}
if(updatePossible)
{
//If we are within the limits then update the global string (for undoing character additions) and the textview
textView.text = temporaryString;
lastSuccessfulViewString = temporaryString;
}
}
Now this won't allow the user to put in their own new line characters, but that could be handled with a couple if then statements.

Answer 2

After a bit of fiddling around, created a control which contains a UITextView as a subview.
I let this control handle the text wrapping and forward the delegate methods to the view registered as a delegate.
It might help others, so I am posting a link to BitBucket here.
PS. It's still very verbose, but that is to show how I solved this for my case.
https://bitbucket.org/depl0y/sbframework/src/master/SBFramework/Views/SBTextView?at=master