Re: Modify Input in NSTableView

FROM : K. Darcy Otto
DATE : Tue Apr 01 02:18:23 2008

Closing in on a solution (but not quite there – see below for 
details):

I have made some progress in solving this problem, but still have one 
strangeness (detailed below).  Here is what I have done to get the ">" 
replaced with "→" in an NSTableView:

1. Set my AppController as the window delegate.
2. Implemented windowWillReturnFieldEditor: as follows:

-(id)windowWillReturnFieldEditor:(NSWindow *)window toObject:
(id)anObject
{
    if ([anObject isKindOfClass:[DeductionTable class]])
    {
        return fieldEditor;
    }
    return nil;
}

(The table in my window is a DeductionTable object, subclass 
NSTableView.  fieldEditor is an object of class 
DeductionTableFieldEditor, a subclass of NSTextField.)

3. I then implement controlTextDidChange as follows:

-(void)controlTextDidChange:(NSNotification *)aNotification
{
   // Trap letters in DeductionTableFieldEditor
   NSMutableString *fieldString = [NSMutableString stringWithString:
[fieldEditor string]];
   NSUInteger changeCount = [fieldString replaceOccurrencesOfString:@">"
                                withString:[NSString stringWithFormat:@"%C",0x2192]
                                   options:NSLiteralSearch
                                     range:NSMakeRange(0,[fieldString length])];
   if (changeCount > 0 && [fieldEditor 
shouldChangeTextInRange:NSMakeRange(0,[fieldString length]) 
replacementString:fieldString])
   {
       [fieldEditor setString:fieldString];
       [fieldEditor didChangeText];
   }
}

So, this creates the result I want: when the user types ">", it is 
automatically replaced by "→".  The problem I'm having is that 
hitting return or tab no longer ends editing of the current cell.  I 
have tried implementing doCommandBySelector: to take care of this, but 
as soon as I do, I lose return, tab and the arrow keys.  Any ideas?

On 31-Mar-08, at 11:26 AM, K. Darcy Otto wrote:
>> On Mar 31, 2008, at 00:29, Quincey Morris wrote:
>>
>> > On Mar 30, 2008, at 23:08, K. Darcy Otto wrote:
>> >
>>
>> >> I'm working on an application in which users enter data into a
>> >> table, but I need to substitute a greater-than symbol (>) for a
>> >> right-arrow symbol (→, unicode: 2192) as the user presses they 
>> key
>> >> (or copies the text, or whatever).  After looking at the docs and
>> >> this list, I'm not much closer to determining the best way to do
>> >> this (or even how to do it).  So far, I have been thinking I have
>> >> to do something with NSWindow and the fieldEditor; perhaps setting
>> >> the window's field editor to be a particular NSTextView, and
>> >> implement some method in that text view  (insertText:?) to make 
>> the
>> >> substitution.  I take it that working with keyDown: would not be
>> >> the best approach.  Would this be on the right track?  Any help
>> >> would be appreciated.
>>
>> >
>> > You could try adding a validate<Key> method for the property that
>> > holds the string value. In that method, take the input string and
>> > create a new string, replacing whatever characters you need to. 
>> Pass
>> > the new string back in the first parameter, and return YES from the
>> > method.
>> >
>> > If I haven't overlooked something obvious, this would work no 
>> matter
>> > whether the text was typed or pasted into the editing field.
>> >
>> > Oh -- make sure you check "Validates immediately" for the table
>> > column binding in IB, too.
>>
>>
>> Of course, this is only going to make the replacement happen when the
>> user presses return or tab. To get it to happen as soon as a
>> replaceable character is typed, you'd have to convince the field
>> editor to validate after every keystroke or editing action. So maybe
>> this is not the best way.

>
> This is exactly the problem I'm running into.  I can get changes to 
> be made after the user exits the editing field, but I cannot get the 
> changes to be made on-the-fly.  After some additional reading, I 
> have tried to solve this problem by implementing the following in 
> the NSWindow delegate (where DeductionTable is my NSTableView 
> subclass, and DeductionTableFieldEditor is my NSTextView subclass):
>
> -(id)windowWillReturnFieldEditor:(NSWindow *)window toObject:
> (id)anObject
> {
>    if ([anObject isKindOfClass:[DeductionTable class]])
>    {
>        return [[DeductionTableFieldEditor alloc] init];
>    }
>    return nil;
> }
>
> Then, I started playing around with -(BOOL)textView:(NSTextView 
> *)aTextView shouldChangeTextInRange:(NSRange)affectedCharRange 
> replacementString:(NSString *)replacementString and -
> (BOOL)textShouldBeginEditing:(NSText *)aTextObject; but all I've 
> succeeded in doing is messing up the editing functions that were 
> there previously.  Any other suggestions?