Question

Possible Duplicate:
Prefixing property names with an underscore in Objective C

iPhone App Developer Beginner here:

in .h

@property (nonatomic, retain) IBOutlet UILabel *detailDescriptionLabel;

in .m

@synthesize detailDescriptionLabel = _detailDescriptionLabel;

I’m used to seeing

@synthesize detailDescriptionLabel;

the = _ is throwing me off, what is this doing?

Answer 1

Each property is backed by an instance variable. The language allows for them to be named differently. By doing @synthesize detailDescriptionLabel = _detailDescriptionLabel;, you’re basically saying that use _detailDescriptionLabel as the backing instance variable for the property detailDescriptionLabel. If you just do @synthesize detailDescriptionLabel;, it implicitly understands that the instance variable has the same name.