COCOA application crashed when trying to get the value from inactive dialog - objective-c

Question

I have created a main dialog (MainMenu.xib) and created two button on mainmenu.xib file and when click on each button, it will launch different xib file(say for button1 xib file is button1.xib and for button2 xib file is button2.xib file).
Now, My question I need the value of button1.xib file into button2.xib file.
I have tried the code
id appDelegate = (AppDelegate*)[[NSApplication sharedApplication] delegate] ;
this code always gives the delegate of active dialog.
Can you please tell me how to get the control or object of inactive dialog?
Thanks,

Answer 1

What you need is model object. Below is really simple approach how you should start. This model object should be stored in AppDelegate for non-document based app. Second window should not know about existence of any other window. The same applies for first window. It shouldn't know more that displaying/working with model.
Accessing model through delegate in fact accessing delegate like below is considered as really, really, really bad.
id model = [(AppDelegate*)[[NSApplication sharedApplication] delegate] model];
Simple example how you can implement model and monitor for changes
#import "AppDelegate.h"
#import "FirstWC.h"
#import "SecondWC.h"
#import "Model.h"
#interface AppDelegate ()
#property (weak) IBOutlet NSWindow *window;
#property (nonatomic, strong) FirstWC *firstWC;
#property (nonatomic, strong) SecondWC *secondWC;
#property (nonatomic, strong) Model *model;
#end
#implementation AppDelegate
- (instancetype)init
{
self = [super init];
if (self) {
_model = [[Model alloc] init];
}
return self;
}
- (IBAction)changeColor:(id)sender
{
NSUInteger number = arc4random() % 4;
switch (number) {
case 0:
self.model.color = [NSColor redColor];
break;
case 1:
self.model.color = [NSColor blueColor];
break;
case 2:
self.model.color = [NSColor purpleColor];
break;
case 3:
self.model.color = [NSColor yellowColor];
break;
default:
break;
}
}
- (IBAction)showFirstWC:(id)sender
{
if (!_firstWC) {
_firstWC = [[FirstWC alloc] initWithModel:self.model];
}
[[_firstWC window] makeKeyAndOrderFront:self];
}
- (IBAction)showSecondWC:(id)sender
{
if (!_secondWC) {
_secondWC = [[SecondWC alloc] initWithModel:self.model];
}
[[_secondWC window] makeKeyAndOrderFront:self];
}
#end
Model:
#import <Cocoa/Cocoa.h>
#interface Model : NSObject
#property (nonatomic, strong) NSColor *color;
#end
#import "Model.h"
#implementation Model
- (instancetype)init
{
self = [super init];
if (self) {
_color = [NSColor blueColor];
}
return self;
}
#end
Window Controller:
#import "FirstWC.h"
#import "Model.h"
#interface FirstWC ()
#property (nonatomic, strong) Model *model;
#end
#implementation FirstWC
- (instancetype)initWithModel:(Model *)model
{
self = [super initWithWindowNibName:#"FirstWC"];
if (self) {
_model = model;
[self addObserver:self
forKeyPath:#"model.color"
options:NSKeyValueObservingOptionInitial | NSKeyValueObservingOptionNew
context:NULL];
}
return self;
}
- (void)windowDidLoad {
[super windowDidLoad];
self.window.backgroundColor = [self model].color;
}
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary<NSString *,id> *)change context:(void *)context
{
if ([keyPath isEqualToString:#"model.color"]) {
self.window.backgroundColor = self.model.color;
}
}
- (void)dealloc
{
[self removeObserver:self forKeyPath:#"model.color"];
}
#end
#import "SecondWC.h"
#interface SecondWC ()
#property (nonatomic, strong) Model *model;
#end
#implementation SecondWC
- (instancetype)initWithModel:(Model *)model
{
self = [super initWithWindowNibName:#"SecondWC"];
if (self) {
_model = model;
[self addObserver:self
forKeyPath:#"model.color"
options:NSKeyValueObservingOptionInitial | NSKeyValueObservingOptionNew
context:NULL];
}
return self;
}
- (void)windowDidLoad {
[super windowDidLoad];
self.window.backgroundColor = [self model].color;
}
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary<NSString *,id> *)change context:(void *)context
{
if ([keyPath isEqualToString:#"model.color"]) {
self.window.backgroundColor = self.model.color;
}
}
- (void)dealloc
{
[self removeObserver:self forKeyPath:#"model.color"];
}
#end

Answer 2

Add properties for both button1 and button2 in your controller, and a (weak) property for button2 in the button1 controller, and vice versa.
- (void)createButtons {
DlgController1 = [[Button1 alloc] initWithWindowNibName:#"Button1"];
DlgController2 = [[Button2 alloc] initWithWindowNibName:#"Button2"];
DlgController1.button2 = DlgController2;
DlgController2.button1 = DlgController1;
}
- (IBAction)Button1:(id)sender {
[DlgController1 showWindow:self];
[NSApp runModalForWindow:DlgController1.window];
[NSApp endSheet:DlgController1.window];
[DlgController1.window orderOut:self];
[DlgController1 close];
}

Answer 3

I have tried the code
id appDelegate = (AppDelegate*)[[NSApplication sharedApplication] delegate] ;
this code always gives the delegate of active dialog.
I'm not quite sure how this relates to the rest of your question, but the above issue suggests that you have an instance of your AppDelegate class in button1.xib and button2.xib. You should not.
There is only one application object in your app. It should have only one delegate. That instance is created in the MainMenu NIB and connected to the application's delegate outlet using the File's Owner placeholder's outlet. That should be the only instance of AppDelegate in your whole app.
If you also create an instance of AppDelegate in the other NIBs, then there will be multiple instances of that class once those NIBs are loaded, which will just confuse things. Also, if those instances are also connected to the application's delegate outlet, then they will replace the original delegate. That explains the symptom you described above where [[NSApplication sharedApplication] delegate] gives an object from the last NIB to load.
I'm not sure what button1.xib and button2.xib are supposed to contain. I'm guessing they are supposed to contain a window. In that case, you should write a custom subclass of NSWindowController to be the window controller for each window NIB. You would instantiate that class in the button's action method and provide it with whatever information it needs (possibly including a reference to the app delegate). That controller class would be responsible for loading the NIB. It would serve as the NIB's owner and would be represented in the NIB by the File's Owner placeholder. It's pretty common to make the window controller be the window's delegate, too. I recommend that you follow the advice of this blog post.