Dynamically hiding columns in a NSTableView

Question

I want to dynamically hide/show some of the columns in a NSTableView, based on the data that is going to be displayed - basically, if a column is empty I'd like the column to be hidden. I'm currently populating the table with a controller class as the delegate for the table.

Any ideas? I see that I can set the column hidden in Interface Builder, however there doesn't seem to be a good time to go through the columns and check if they are empty or not, since there doesn't seem to be a method that is called before/after all of the data in the table is populated.

Answer 1

I don't have a complete answer at this time, but look into Bindings. It's generally possible to do all sorts of things with Cocoa Bindings.

There's no Visibility binding for NSTableColumn, but you may be able to set the width to 0.

Then you can bind it to the Null Placeholder, and set this value to 0 - but don't forget to set the other Placeholders to reasonable values.

(As I said, this is just a start, it might need some tweaking).

Answer 2

There is no one time all the data is populated. NSTableView does not store data, it dynamically asks for it from its data source (or bound-to objects if you're using bindings). It just draws using data it gets from the data source and ditches it. You shouldn't see the table ask for data for anything that isn't visible, for example.

It sounds like you're using a datasource? When the data changes, it's your responsibility to call -reloadData on the table, which is a bit of a misnomer. It's more like 'invalidate everything'.

That is, you should already know when the data changes. That's the point at which you can compute what columns should be hidden.

Answer 3

I've done this with bindings, but setting them up programmatically instead of through Interface Builder.

This psuedo-snippet should give you the gist of it:

NSTableColumn *aColumn = [[NSTableColumn alloc] initWithIdentifier:attr];
[aColumn setWidth:DEFAULTCOLWIDTH];
[aColumn setMinWidth:MINCOLWIDTH];
[[aColumn headerCell] setStringValue:columnLabel];

[aColumn bind:@"value"
     toObject:arrayController 
  withKeyPath:keyPath 
  options:nil];    

[tableView addTableColumn:aColumn];
[aColumn release];

Of course you can add formatters and all that stuff also.

Answer 4

@amrox - If I am understanding your suggestion correctly, you're saying that I should bind a value to the hidden property of the NSTableColumns in my table? That seems like it would work, however I don't think that NSTableColumn has a hidden property, since the isHidden and setHidden messages control the visibility of the column - which tells me that this isn't a property, unless I'm missing something (which is quite possible).

Answer 5

A NSTable is just the class that paints the table. As you said yourself, you have some class you give the table as delegate and this class feeds the table with the data to display. If you store the table data as NSArray's within your delegate class, it should be easy to find out if one column is empty, isn't it? And NSArray asks your class via delegate method how many columns there are, so when you are asked, why not looking for how many columns you have data and report that number instead of the real number of columns you store internally and then when being asked for providing the data for (column,row), just skip the empty column.