Question

Possible Duplicates:
How does an underscore in front of a variable in a cocoa objective-c class work?
Prefixing property names with an underscore in Objective C

Why do a lot of Objective-C programmers put underscores before instance variables (even if they never even access them directly anywhere from their code)? What’s the logic behind that?

Answer 1

The logic is to make it clear when accessing the property vs accessing the ivar.

You can’t mistakenly access the raw ivar without the property if its underscored. I don’t do this in my own code though.