NSTextView string is null when calling from an other class - objective-c

Question

I'm a newbie in Cocoa
I have a function in a class call TextSaver.m :
- (void) save {
TheNotes *myNote = [[TheNotes alloc]init];
myNote.theText = [theTextView string];
NSLog(#"%#",myNote.theText);
[NSKeyedArchiver archiveRootObject:myNote.theText toFile:#"..."];
}
And I'm calling it from the AppDelegate with applicationWillTerminate :
- (void)applicationWillTerminate:(NSNotification *)notification{
[theTextSaver save];
}
But NSLog(#"%#",myNote.theText); results null... Like NSLog(#"%#",theTextView);. Which means when I call the function I can't access theTextView.
I've already try to call this function in the TextSaver.m class with a -(IBAction) and it worked!
Hope you can help me !
EDIT
The TextSaver is created with an #import TextSaver.h and in the appInterface
TextSaver *theTextSaver;
EDIT 2
I rewrite the code to make it simpler :
AppDelegate.h :
#import <Cocoa/Cocoa.h>
#import "TheNotes.h"
#interface AppDelegate : NSObject <NSApplicationDelegate>{
TheNotes *myNote;
}
#property (copy) TheNotes *myNote;
#property (assign) IBOutlet NSWindow *window;
#end
AppDelegate.m :
#import "AppDelegate.h"
#implementation AppDelegate
#synthesize myNote;
- (void)applicationDidFinishLaunching:(NSNotification *)aNotification{
myNote = [[TheNotes alloc]init]; //Do I need to put it in -(id) init ?
}
- (void)applicationWillTerminate:(NSNotification *)notification{
[myNote save];
}
#end
TheNotes.h :
#import <Foundation/Foundation.h>
#interface TheNotes : NSObject {
NSString *theText;
IBOutlet NSTextView *theTextView;// Do I need to alloc memory ?
}
-(void) save;
#property (copy) NSString *theText;
#end
TheNotes.m :
#implementation TheNotes
#synthesize theText;
- (void) save {
NSLog(#"%#",theTextView.string);// Save is properly called, but this results (null).
[NSKeyedArchiver archiveRootObject:theTextView.string toFile:#"..."];
}
#end

Answer 1

The two questions you need to answer for yourself are:
Why do I expect my TextSaver to know about the text view?
Where do I tell the TextSaver about the text view?
The other possible answer to the first question is “the TextSaver created the text view”, but I'm assuming that's not the case.
So, you need to find where you think you're telling the TextSaver about the text view and make sure that's the case.
If you haven't done anything specific to tell the TextSaver about the text view, but rather are expecting it to just know about it, then that's probably the problem.
As Phillip Mills alluded to in his comment, merely declaring a variable named theTextView does not mean that the TextSaver knows about the text view. The compiler cannot read English: the names you choose are for your own benefit only; the compiler treats them only as identifiers. It does not see “theTextView” and go “oh, that! that's over there; I'll go get it”.
In order for theTextView to actually point to the text view, you need to put the text view there. You do this via assignment. Either expose theTextView as a property and set it from somewhere else, or set it internally within the TextSaver class (after either creating the text view yourself or getting it from another object).
I would make it a property (named simply textView) and set that property from whatever owns both the TextSaver and the text view.

Answer 2

This is a working example of basically what you're trying to achieve, HTH.
There are two classes, AppDelegate and TestViewController. TestViewController has a UITextView, whenever the user presses the home button of the device while editing the UITextView, the - (void)applicationDidEnterBackground:(UIApplication *)application method of the AppDelegate is called and the note is printed to the console (here you could save the note instead).
I use applicationDidEnterBackground because it's what is called when the app goes into background mode.
AppDelegate.m
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
PVSTestViewController *nextScreen = [[PVSTestViewController alloc] init];
self.delegate = nextScreen; // Assign TestViewController as the AppDelegate's delegate.
self.window.rootViewController = nextScreen;
[self.window makeKeyAndVisible];
return YES;
}
- (void)applicationDidEnterBackground:(UIApplication *)application
{
[self.delegate saveData]; // Called when the user presses the home button.
}
AppDelegate.h
....
#protocol PVSAppDelegateProtocol <NSObject>
- (void)saveData; // Any class that conforms to our protocol must implement this method.
#end
#interface PVSAppDelegate : UIResponder <UIApplicationDelegate>
#property (strong, nonatomic) UIWindow *window;
#property (nonatomic, weak) id<PVSAppDelegateProtocol> delegate; // Here we store the delegate class.
#end
TestViewController.m
#import "PVSTestViewController.h"
#interface PVSTestViewController ()
#property (weak, nonatomic) IBOutlet UITextView *textView;
#end
#implementation PVSTestViewController
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
return self;
}
- (void)viewDidLoad
{
[super viewDidLoad];
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
}
- (void)saveData
{
// This is called by the AppDelegate when the app goes into the background.
NSLog([NSString stringWithFormat:#"Text is: %#", self.textView.text ]);
}
#end
TestViewController.h
....
#import "PVSAppDelegate.h"
#interface PVSTestViewController : UIViewController <PVSAppDelegateProtocol>
#end