Re: A documentation dumdum

FROM : Jeff LaMarche
DATE : Sun Jun 22 18:13:45 2008

On Jun 22, 2008, at 12:02 PM, William Squires wrote:

> okay, looking up tableView:setObjectValue:forTableColumn:row shows 
> that setObjectValue: takes an (id), but what is it really? An 
> NSString pointer? I want to get an NSString that represents the new 
> value the user typed in for the selected (and edited) cell in the 
> NSTableView. Can I safely typecast this to (NSString *)? In which 
> case, maybe the docs should say that this is an (NSString *) instead 
> of (id)?


The documentation is correct. The Table View Programming Guide states:

The NSTableView object treats objects provided by its data source as 
values to be displayed in NSCell objects. If these objects aren’t of 
common value classes—such as NSString, NSNumber, and so on—you may 
need to create a custom NSFormatter object to display them. For more 
information, see Data Formatting Programming Guide for Cocoa.

In other words, it's not always going to be an NSString *. Whatever 
the object is, it will be converted to a string for display, but the 
table view is actually capable of holding different types of data and 
doesn't change the type that it's holding, so you can't assume that 
the object it holds is a string. Now, if you are giving the table 
strings, then by all means, cast the object to an NSString. If you're 
not sure what the type of object you're getting back is, you can find 
out in the debugger console by typing

po [returnedValue class]

or adding an NSLog statement to your code like

NSLog(@"returned value class: %@", [returnedValue class]);

HTH