Question

I am making a simple mac app in which i want to switch windows.
I have two NSWindowController class MainWindow and DetailWindow

I am using this code :

MainWindow class:

//MainWindow.h
@class DetailWindow;
@interface MainWindow : NSWindowController{

    IBOutlet NSButton *btn1;
    DetailWindow *detailwindow;
}
@property (nonatomic, retain) IBOutlet NSButton *btn1;
- (IBAction)btn1Event:(id)sender;

//MainWindow.m

@implementation MainWindow
@synthesize btn1;

- (IBAction)btn1Event:(id)sender {

if (!detailwindow) {
    detailwindow = [[DetailWindow alloc] initWithWindowNibName:@"DetailWindow"];

}
    [detailwindow showWindow:self];
}
@end

DetailWindow Class:

//DetailWindow.h
@class MainWindow;
@interface DetailWindow : NSWindowController{

    IBOutlet NSButton *backbtn;
    MainWindow *mainwindow;
}
@property (nonatomic, retain) IBOutlet NSButton *backbtn;
- (IBAction)back:(id)sender;

//DetailWindow.m

@implementation DetailWindow
@synthesize backbtn;

- (IBAction)back:(id)sender {

if (!mainwindow) {
    mainwindow = [[MainWindow alloc] initWithWindowNibName:@"MainWindow"];

}
    [mainwindow showWindow:self];
}
@end

Now the problem is when i click backbtn on DetaiWindow it will open a new MainWindow.
So i have two MainWindow on screen.
I want just main window at front when i click backbtn.

Any help??

Thank you..!!

Answer 1

Your basic problem is that each window is assuming that it is its own job to create the other. Each has an ivar for the other, but there’s no external access to it — via a property or being an IBOutlet or anything else — so it always starts out as nil, and a new copy gets created instead of reusing the old one.

There are any number of ways to get around this. Probably the easiest would be to create both windows in Interface Builder and link them up there, having made the ivars IBOutlet. Then you know you never have to create them in code at all.

However, purely on the basis of inertia, here’s an alternative that sticks closer to what you’ve got already. Note that I’ve assumed for simplicity that mainWindow always exists first. If not, you’ll have to duplicate the process the other way around.

//MainWindow.h
@class DetailWindow;
@interface MainWindow : NSWindowController
{

    IBOutlet NSButton *btn1;
    DetailWindow *detailwindow;
}
@property (nonatomic, retain) NSButton *btn1;
- (IBAction)btn1Event:(id)sender;

//MainWindow.m

@implementation MainWindow
@synthesize btn1;

- (IBAction)btn1Event:(id)sender
{
    if (!detailwindow)
    {
        detailwindow = [[DetailWindow alloc] initWithWindowNibName:@"DetailWindow"];

        // having created the other window, give it a reference back to this one
        detailWindow.mainWindow = self;
    }

    [detailwindow showWindow:self];
}
@end

//DetailWindow.h
@class MainWindow;
@interface DetailWindow : NSWindowController
{

    IBOutlet NSButton *backbtn;
    MainWindow *mainwindow;
}
@property (nonatomic, retain) NSButton *backbtn;

// allow the main window to be set from outside
@property (nonatomic, retain) MainWindow *mainWindow;
- (IBAction)back:(id)sender;

//DetailWindow.m

@implementation DetailWindow
@synthesize backbtn;
@synthesize mainWindow;

- (IBAction)back:(id)sender
{
    // no window creation on the way back
    NSAssert(mainWindow, "mainWindow not set!");
    [mainwindow showWindow:self];
}
@end

Untested, so usual caveats apply.