What is the basic difference between NSTimer, NSTask, NSThread and NSRunloop?

Question

What is the difference between NSTimer, NSTask, NSThread and NSRunloop and is there a guideline on when to use each of them?<

Answer 1

• NSTimer is a timer object, a way to invoke a selector on an object in the future.
• NSThread is a thread class. I suppose you know what a thread is.
• NSTask is a process class, a way to run another program from your program.
• NSOperation (I'm adding to the question) is a very nice abstraction for a single task. You embed your operation in this class and you can easily execute concurrently by means of an NSOperationQueue class.
• NSRunLoop is the most difficult to understand. In some way abstracts and adapts the select() unix system call, managing input sources and dispatching events and timers on a thread.

The guideline is the Apple Threading Programming Guide.