Objective C class and RESTful API

I've never built an iOS app, so I need some feedback on the following.

When building your app do you create an objective c class to model the table that you have in your relational database? So lets say I have this table:

Todo Item 
- title
- completed

Would I create an objective c class that looks like this

@interface TodoItem : NSObject 
@property NSString *title;
@property BOOL completed;
@end

Do any validation required then create my request url from my objective c class?

POST: http://ift.tt/1zsg6AN

To create my item on my database?