Core Data fetchedresultscontroller question : what is "sections" for?

Posted by Jake on Stack Overflow See other posts from Stack Overflow or by Jake
Published on 2010-05-11T08:46:05Z Indexed on 2010/05/11 9:04 UTC
Read the original article Hit count: 391

Filed under:

core-data

|

objective-c

|

iphone

|

cocoa

Hi, I'm trying to get to know Core Data (I'm a noob at iPhone development) and in order to do this I'm trying to get an object from the fetchedresultscontroller and NSlog it's name (a property of the object). I tried to do it like this:

NSArray *ar = [NSArray arrayWithArray:[fetchedResultsController sections]];
Task *t = [ar objectAtIndex:0];
NSLog(@"%@", t.taskName);

However, the app crashed with this error: the app crashes with the error

Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '* -[_NSDefaultSectionInfo taskName]: unrecognized selector sent to instance 0x3d1f670'

I have since learned that you need to use the fetched objects property for this, but then what is sections for? Thanks for any help, sorry if this is a supremely stupid question. I've looked over the documentation but still don't understand.

© Stack Overflow or respective owner

Related posts about core-data

Records not being saved to core data sqlite file

as seen on Stack Overflow - Search for 'Stack Overflow'
I'm a complete newbie when it comes to iOS programming and much less Core Data. It's rather non-intuitive for me, as I really came into my own with programming with MATLAB, which I guess is more of a 'scripting' language. At any rate, my problem is that I had no idea what I had to do to create a… >>> More
iPhone - Core Data crash on migration

as seen on Stack Overflow - Search for 'Stack Overflow'
I have problems, when i install app from Xcode all works but if I build app and install it from iTunes I have an error with the database at launch. This happens only than i have changes in the core data model and need to migrate to a new version. At first launch at crashes with message: Thread 0: 0… >>> More
CoreData update problems

as seen on Stack Overflow - Search for 'Stack Overflow'
My app makes updates in background thread then saves context changes. And in main context there is a table view that works with NSFetchedResultsController. For some time updates work correctly, but then exception is thrown. To check this I've added NSLog(@"%@", [self.controller fetchedObjects]); to… >>> More
Core Data managed object context thread synchronisation

as seen on Stack Overflow - Search for 'Stack Overflow'
I'm have an issue where i'm updating a many-to-many relationship in a background thread, which works fine in that threa, but when I send the object back to the main thread the changes do not show. If I close the app and reopen the data is saved fine and the changes show on the main thread. Also using… >>> More
UITableView Core Data reordering

as seen on Stack Overflow - Search for 'Stack Overflow'
I know this question has been asked before, and I took a look at the answer to this question. However, I'm still confused as to how to implement reordering with a UITableView in a Core Data project. What I know is that I need to have a "displayOrder" attribute in my Entity to track the order of items… >>> More

Related posts about objective-c

Blocking access to websites with objective-C / root privileges in objective-C

as seen on Stack Overflow - Search for 'Stack Overflow'
I am writing a program in Objective-C (XCode 3.2, on Snow Leopard) that is capable of either selectively blocking certain sites for a duration or only allow certain sites (and thus block all others) for a duration. The reasoning behind this program is rather simple. I tend to get distracted when I… >>> More
Objective-C with some Objective-C++, calling a normal c++ method "referenced from" problem

as seen on Stack Overflow - Search for 'Stack Overflow'
Hi, I made an Objective-C project for the iPhone. I had only one cpp class, the soundEngine taken from some Apple demo. Now I'm trying to merge OpenFeint which is coded in Objective-C++. As soon as I drop in the code without even referring to it from my code, when I hit Build, my Objective-C code… >>> More
Add an objective @property attribute in objective-c

as seen on Stack Overflow - Search for 'Stack Overflow'
Does anyone know of a way to add additional attribute types to the @property keyword without modifying the compiler? Or can anyone think of another way to genericize getter/setter creation? Basically, I have a lot of cases in a recent project where it's handy for objects to lazily instantiate their… >>> More
ObjectiveC Syntax for Specifying Protocol Name in Method Argument

as seen on Stack Overflow - Search for 'Stack Overflow'
What's the ObjectiveC syntax for specifying a protocol as an argument in a method? Say I have 2 protocols, MyProtocol and MyProtocolCB: @protocol MyProtocolCB <NSObject> - (void) func; @end @protocol MyProtocol <NSObject> - (void) register:(MyProtocolCB*) cb; @end I'm receiving this… >>> More
ObjectiveC builtin template system ?

as seen on Stack Overflow - Search for 'Stack Overflow'
I am developing an iPhone application and I use HTML to display formatted text. I often display the same webpage, but with a different content. I would like to use a template HTML file, and then fill it with my diffent values. I wonder if ObjectiveC has a template system similar to ERB in Ruby. That… >>> More