how to reach model from different view controllers? - ios

Question

i'm not new to OOP but i'm very new to objective c and i've been having trouble with reaching model from two different view controllers, one to set it the other to get the data. Here's my model:
#import <Foundation/Foundation.h>
#interface ModelUnit : NSObject{
NSString * nickname;
int total;
}
- (void)setTotal:(int)newTotal;
- (void)setName:(NSString *)nick;
- (NSString *)getName;
#end
#import "ModelUnit.h"
#implementation ModelUnit
- (void)setTotal:(int)newTotal{
total = newTotal;
}
- (void)setName:(NSString *)nick{
nickname = nick;
}
- (NSString *)getName{
return nickname;
}
#end
Here's how i try to set nickname in the initial viewcontroller:
//.h
#interface introViewController : UIViewController{
ModelUnit * modl;
}
-(ModelUnit *) modl;
-(IBAction)nickEntered:(UITextField *)sender;
#end
//.m
-(ModelUnit *) modl{
if(!modl){
modl = [[ModelUnit alloc] init];
}
return modl;
}
- (IBAction)nickEntered:(UITextField *)sender{
[[self modl] setName:[sender text]];
ViewController *vew = [[ViewController alloc] initWithNibName:nil bundle:nil];
[self presentViewController:vew animated:NO completion:Nil];
}
And here is how i try to receive and display it in the last viewcontroller:
- (void)viewDidLoad
{
[super viewDidLoad];
introViewController *pnt = [[introViewController alloc] initWithNibName:nil bundle:nil];
[display setText:[[pnt modl] getName]];
}
But it always prints it as null when i NSlog it to the console. I know it's a very novice question but i'm completely stuck. Thanks for any help.

Answer 1

It's because each of your UIViewController instances are referencing different instances of your model class (actually, a non-instance in the second case).
Make an #property in your "last" view controller (class name of "ViewController" it would seem), something like:
#property (strong, nonatomic) Model *model;
Then, when pushing your second view controller, set its model property, like this:
ViewController *vew = [[ViewController alloc] initWithNibName:nil bundle:nil];
vew.model = self.modl;
[self presentViewController:few animated:NO completion:NULL];
That way, you're passing around the same instance of your Model class. The way you're doing it, you're trying to access a property that was never initialized, which is why you're getting nil.

Answer 2

If you're not new to OOP, you should quite easily see the mistake you're making. You're trying to retrieve a value out of an object you just initialized.
Where you need to pass the data is in the first object as you initialized the second object.
Between this line:
ViewController *vew = [[ViewController alloc] initWithNibName:nil bundle:nil];
And this line:
[self presentViewController:vew animated:NO completion:Nil];
You're still in the first object and you hold a reference to the second object. Give the ViewController class (a better name and) a NSString property to hold the data the getName method returns. And then set that property between the two lines I posted.
Also, Objective-C doesn't name their getters with get.