"description" is a method on NSObject that returns a textual description of an object, and what you're seeing is the default implementation (which just prints the address).
That implies that you don't have a method implemented that overrrides "description" to returns something else.
Without seeing what ObrasData's implementation looks like, it's hard to guide you more.
Edit, having seen the implementation I see that you have a property called "descripcion" (in Spanish) that you initialise in the init method. I assume then that you actually want to do this:
[self.detailItem descripcion]
If, on the other hand you really do want to describe the whole object then you need to override the description method e.g.
- (NSString *)description
{
return [NSString <create your description yourself here>];
}