Question

I have a Cocoa project with an object that holds information from a SQLite database.
By now the information is stored in memory by this object and is used in the user interface to read and write new information.
But now I came to a small problem… I decided to create a new controller class to handle the actions of an NSTableView and I want to access this same database object that was declared elsewhere.
Which is the best option to access this information? I wish to avoid loading the information more than once in memory and also avoid use pure C/C++ codes with global variables.

It is better to understand my point by looking at the code.
I accept other solutions as well, naturally.

My idea of code is currently like this:

FirstClass.h

#import <Foundation/Foundation.h>
#import "DatabaseModel.h"

@interface FirstClass : NSObject {

    IBOutlet NSScrollView *informationListTable;
    NSMutableArray *informationList;

}
@end

FirstClass.m

#import "FirstClass.h"

@implementation FirstClass

- (void)awakeFromNib{
    DatabaseModel *list = [[DatabaseModel alloc] init];
    informationList = [[NSMutableArray alloc] initWithArray:[list loadList]];
    [list release];
    [machinesListTable reloadData];
}

SecondClass.h

#import <Foundation/Foundation.h>

@interface SecondClass : NSObject {
    IBOutlet NSTextField *labelName;
    NSString *name;
}

- (IBAction)showName:(id)sender;

@end

SecondClass.m

#import "FirstClass.h"
#import "SecondClass.h"
@implementation SecondClass

- (IBAction)showName:(id)sender{
/*
Here name must get something like:

[[FirstClass.informationList objectAtIndex:3] name]

Here labelName must display name.
*/

}

@end

Answer 1

you can either create the object once then pass the object around, with each controller retaining it as needed. Or you can use a singleton instance. I would say the singleton instance is easier to read, but it depends on the application