I have a question about how to access the data in core data from a custom object.
I have been successful at doing the following: (1) creating a core data entity using the graphical interface in xcode. I am calling the entity “Points” and each point has the attributes “name” (a string), “x” (an int 16), and “y” (an int 16). (2) creating a table and a plus/minus button to add and modify this core data using interface builder. (3) adding an array and bindings to the table and plus/minus buttons so that the data is correctly stored and shown.
I have created a custom view that I can successfully draw in as well. What I would like to know is what code can I use in the drawRect method in my custom view to access the data stored in the core data part of my program. I would like to be able to get all of the points in the table and use their x and y values to plot them in the custom view. How do I get this data?
Have a look at the docs for NSArrayController. You can access all your objects from it.
I have looked into it, but it looks like there are two possibilities for getting the information from core data through the NSArrayController:
(1) Adding custom bindings to my custom view. The NSTableView allows you to bind the values of the columns to an NSArrayController through the “value” bindings. A custom view only has “hidden” and “toolTip” as possible bindings. I wish I could get IB to show a Points binding for my custom view that would allow me to get the array of points from my PointController (which is an NSArrayController). I think this is possible, but I have not been successfull at figuring out how to do it.
(2) Programmatically getting the data from the NSArrayController from within my custom view. If only there was a way to say something like “NSArray *array = [PointController getArrayOfPoints];”. Then I could use an enumerator to go through and plot all of the points with their respective x and y values. I could even draw the name under each point.
Anyone have any idea of how to do either of the top two things?
Another option, and probably the best for your situation, is to have your controller– be it an NSDocument subclass, NSWindowController subclass, or some other sort of controller class– bind the arrangedObjects of the NSArrayController to some ‘values’ array on your view, and then have your view get the objects it needs to work with from there.
Anyone have any idea of how to do either of the top two things?
Yes:
http://www.devworld.apple.com/documentation/Cocoa/Conceptual/CoreData/index.html
and
http://developer.apple.com/documentation/Cocoa/Conceptual/CocoaBindings/index.html