How to update NSTableView without using -reloadData?

Question

I am new to the Mac. I am trying to update a particular cell in NSTableView without using -reloadData, as -reloadData updates the whole table. I have tried everything but all was in vain. I am trying to do something similar to what we used to do in CListCtrl in MFC or in .NET.

Solution 1

Have a look at reloadDataForRowIndexes:columnIndexes: method. To update a single cell the following should work:

[yourTable reloadDataForRowIndexes:[NSIndexSet indexSetWithIndex:row]  
                     columnIndexes:[NSIndexSet indexSetWithIndex:column]];

Solution 2

This is a fundamental difference between the way views typically work in Cocoa and how they work in some other frameworks. NSTableView does expose a -reloadDataForRowIndexes:columnIndexes: API, as Vladimir points out, but you'll notice the absence of a "withObject:" parameter.

This is because Cocoa views and controls are not designed to also act as data containers. Rather, they're for presentation of and interaction with data that is managed by some other model object, usually through an intermediate controller of some sort.

Given a table view, for example, if your model has informed your controller that some particular data has changed, the controller can invalidate the displayed portion of the table that maps to that value - if there even is a displayed portion of the table. The next time it draws itself, the table will ask its data source (the controller) for the values to present for the area it needs to redraw.

Thus despite a superficial similarity in user interaction, you'll probably want to reconsider how you write the code to implement your user interface. You'll wind up with much more factored Model-View-Controller style code in the end; the price is that you'll need to actually represent your model more thoroughly than you might have had to in frameworks that didn't require such a separation of concerns.

Solution 3

A full example of using reloadDataForRowIndexes to update all rows but only a single column:

int col = 2 ;
[self.myTable reloadDataForRowIndexes:
    [NSIndexSet indexSetWithIndexesInRange:
        NSMakeRange(0,self.myTable.numberOfRows)] 
    columnIndexes:
        [NSIndexSet indexSetWithIndex:col]
];

Or all columns for a single row:

int row = 2 ;
[self.myTable reloadDataForRowIndexes:
    [NSIndexSet indexSetWithIndex:row]
columnIndexes:
    [NSIndexSet indexSetWithIndexesInRange:NSMakeRange(0, self.myTable.numberOfColumns)]
];

Comments

[Omayr]

I want to do this because of efficiency. Like I need to update 8-10 cells per second it this case I dont want the whole table to be updated over and again !

[Michael Teper]

Docs link: developer.apple.com/library/mac/documentation/Cocoa/Referenc‌​e/…:

[Matt]

While this is the correct solution it should be mentioned that reloadData() also just re-renders the currently visible cells and not the entire table.

[TheNextman]

In your second example, reloadDataForRowIndexes:columnIndexes: can't take an NSRange, so you need to do something like: [NSIndexSet indexSetWithIndexesInRange:NSMakeRange(0, _tableView.numberOfColumns)]