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Convert to absolute value in Objective-C

How do I convert a negative number to an absolute value in Objective-C? i.e. -10 becomes 10?

iPhone SDK difference between isKindOfClass and isMemberOfClass

Can any one tell me what the difference is between the isKindOfClass:(Class)aClass and the isMemberOfClass:(Class)aClass functions? I know it is something small like, one is global while the other is an exact class match but I need someone to specify which is which please.

CFNetwork and Bonjour integration for iPhone to Mac integration

I want to use CFNetwork and Bonjour in conjunction to be able to have communications between my iPhone app and a Mac app. The app on the iPhone would have one button. Then on the Mac app, there will be a label. If the button is pushed on the iPhone app, the label changes on […]

Using -performSelector: vs. just calling the method

I’m still kind of new to Objective-C and I’m wondering what is the difference between the following two statements? [object performSelector:@selector(doSomething)]; [object doSomething];

How to check if an NSDictionary or NSMutableDictionary contains a key?

I need to check if an dict has a key or not. How?

NSPredicate: filtering objects by day of NSDate property

I have a Core Data model with an NSDate property. I want to filter the database by day. I assume the solution will involve an NSPredicate, but I’m not sure how to put it all together. I know how to compare the day of two NSDates using NSDateComponents and NSCalendar, but how do I filter […]

iPhone proper usage of Application Delegate

I’m looking to be able to reference certain state/objects through anywhere in my application. For instance, a user logs in to their application, I need to call a web service and retrieve the users information. Then I want to be able to access this information from anywhere in the application with something like the following: […]

Best way to implement Enums with Core Data

What is the best way to bind Core Data entities to enum values so that I am able to assign a type property to the entity? In other words, I have an entity called Item with an itemType property that I want to be bound to an enum, what is the best way of going […]

Set a custom subclass of UINavigationBar in UINavigationController programmatically

Does anyone know how can I use my custom subclass of UINavigationBar if I instantiate UINavigationController programmatically (without IB)? Drag a UINavigationController in IB show me an under Navigation Bar and using Identity Inspectory I can change class type and set my own subclass of UINavigationBar but programmatically I can’t, navigationBar property of Navigation Controller […]

Block Declaration Syntax List

Block syntax in Objective C (and indeed C, I presume) is notoriously incongruous. Passing blocks as arguments looks different than declaring blocks as ivars, which looks different than typedefing blocks. Is there a comprehensive list of block-declaration syntax that I could keep on hand for quick reference?