Re: Hiding Rows in NSTableView

FROM : Frank Midgley
DATE : Mon Apr 18 23:32:55 2005

On Apr 18, 2005, at 1:13PM, Jason Taylor wrote:

> I am writing a program that has a table of items, each with a check
> box. If the check box is checked off, the item is considered complete,
> like an item of a todo list. The user has the option to hide checked
> off items when displaying the table. My code is setup such that when a
> user checks off an item, the object at the row that was checked off is
> set to 'completed'. When the table is reloaded, the items that are
> checked off will not show up. In the tableView:
> objectValueForTableColumn:row datasource method, I check each object
> of my data source array to see if it is 'completed'. If it is not, I
> display it, otherwise I don't. The problem is that once I hide an
> item, the row indexes of the table no longer match the row indexes of
> my data source array (for instance hiding the first item in the table
> with row index 0 will hide the object in my data source array with
> index 0, this is fine, but when the table is reloaded that first
> element of the data source array is not displayed so the object at row
> index 0 in the table is actually the object at index 1 in my array). 
>  Is there a way to just hide a row in an NSTableView or will I have to
> subclass it? Does anyone know of any code that does this so I can use
> it as a reference?


Once a table view has asked how many rows are in the table then that is
how many rows will be displayed.  It assumes there is a one-to-one
mapping between the rows and the entries in the data source.

Two options:

1. Make your data source methods smart enough to hide the hidden rows. 
For example, the tableView:objectValueForTableColumn:row can't just get
the object at the specified row index from the data source.  It will
have to manually walk through the array (or whatever it is) and count
how many visible items it comes across.  Since the data source methods
get called a lot, a faster implementation that pre-calculated the row
index to array index mapping for all possible rows would be much
better.

2. Only include the visible rows in your data source.  When the user
chooses to only show the uncompleted items then remove the completed
ones from the data source and store them in a separate container
(array, dictionary, whatever).  Replace them when the user toggles the
setting back.  Far simpler coding then the previous option.

-Frank

------------------------------------
Frank M. Midgley
<email_removed>
http://homepage.mac.com/knarf/