On 10 Dec 2008, at 12:21 pm, Randall Meadows wrote:
I could use a little guidance, please, on customizing cells for
display in an NSTableView. (My app is Leopard-only.) I looked
around the Apple docs and cocoadev, but didn't really find anything
useful. Other pointers would be appreciated.
My table has but one column, but each cell in that column is made up
of 2 or more views. I think I have what I need as far as the cells
go, but it's feeding them to the table view that's giving me problems.
The first thing to realise is that there is not one cell per row.
There is only one cell per column. The single cell is "moved" from row
to row as the table draws the rows. Once you realise that there is
only one cell, things become a bit clearer.
I'm not sure what you mean by each cell having two views. Do you
literally mean NSViews, or are you using the term more loosely? AFAIK,
it's really not feasible to embed actual NSViews in a cell.
I know the "required" datasource methods are -
numberOfRowsInTableView: and -
tableView:objectValueForTableColumn:row:; the first is a no-brainer,
the 2nd one stumps me.
The second one gets the actual value for the row/column in question.
Without this your table wouldn't draw anything because it doesn't know
what to draw - the table is entirely generic and makes no assumptions
about what the data content is.
Because there is only one cell per column, this method is used
whenever needed to give the data to the cell at the right time.
I assume I must implement -tableView:dataCellForTableColumn:row: to
feed the table my custom cells for each row, right?
Not normally. This method is used when you have different cell types
for each row, which is fairly uncommon. Typically you set the cell for
the entire column in one go. You can do this in IB, or else
programatically using [NSTableColumn setDataCell:]
What purpose then does the -tableView:objectValueForTableColumn:row:
method serve? What should be returned from that if I'm already
feeding ready-made cells from the other one? (This table is not
editable, so I do not need to worry about -
tableView:setObjectValue....)
Don't feed cells per row unless you have to. Set the cell once for the
column, then let the dataSource supply it on demand with its data.
The docs also say that my cells must "properly" implement -
copyWithZone:, but I don't know what "properly" means in that context.
I guess it means that your copy method must return a real copy, not
just retain and return self, since cells are considered always mutable
- the table must be allowed to mutate the cell as needed with no side
effects.
hth,
Graham
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