Re: Problems with NSCell setObjectValue
Re: Problems with NSCell setObjectValue
- Subject: Re: Problems with NSCell setObjectValue
- From: Quincey Morris <email@hidden>
- Date: Sat, 21 Aug 2010 23:53:29 -0700
On Aug 21, 2010, at 23:24, Hrishikesh Murukkathampoondi wrote:
>> The 'dataCellForTableColumn:...' delegate method is intended to return a data cell for the >table column to use>, but *not* to configure the cell value for the specific row it's going >to represent. Remember that the object val>ue comes from the data source object, not the del>egate object, and it's therefore wrong for the delegate objec>t to try to supply the value.
> I don't understand your answer.
> The documentation for -tableView:dataCellForTableColumn:row: says
> "A different data cell can be returned for any particular table column and row, or a cell that will be used for the entire row (a full width cell)."
> What I am trying to do is to display multiple text items arranged in a custom format. For that purpose I use this delegate method to return my "custom cell" wherein I have modified drawWithFrame:inView: to do my custom drawing.
> From the documentation I understand that this delegate method is used to return an NSCell subclass. This subclass can include a custom method to draw the cell.
The cell is OK -- there's nothing wrong with the cell.
But it's wrong to use 'setObjectValue:' in 'tableView:dataCellForTableColumn:row:'. Here's the sequence of events:
#1. The table view calls the delegate's 'tableView:dataCellForTableColumn:row:' to get the cell for the row and column.
#2. The table view calls the data source's 'tableView:objectValueForTableColumn:row:' to get the object value for the row and column.
#3. The table view sets that object value in the cell, using 'setObjectValue:'.
#4. The table view causes the newly-configured cell to be drawn.
So, setting the object value in #1 doesn't achieve anything useful.
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