## Using Blocks (i.e. Closures) To Improve Transactional Code

on November 21st, 2010 by Tom 4 Comments Cocoa

This article will be about using blocks to improve transactional code. When I say "transactional" code, I mean code that has an opening, a middle, and a closing, where the opening and the closing have to be matched. You see it in a few places in Cocoa, such as:

• KVO:
1. willChangeValueForKey:
2. change the value
3. didChangeValueForKey:
• NSGraphicsContext:
1. saveGraphicsState
2. do some drawing
3. resoreGraphicsState
• NSFileWrapper:
1. open a file
2. read/write to it
3. close the file

I’m going to show you a "before and after" comparison of a function that uses NSGraphicsContext and NSAffineTransformation.

## How Cocoa Bindings Work (via KVC and KVO)

on November 5th, 2010 by Tom 8 Comments Cocoa

Cocoa bindings can be a little confusing, especially to newcomers. Once you have an understanding of the underlying concepts, bindings aren’t too hard. In this article, I’m going to explain the concepts behind bindings from the ground up; first explaining Key-Value Coding (KVC), then Key-Value Observing (KVO), and finally explaining how Cocoa bindings are built on top of KVC and KVO.