Cocoa, Objective- C how correctly pass params from one window to another

Question

I'm really new in Cocoa/Obj-C programming.

I have fairly simple app (target platform Mac OSX 10.5 & 10.6), my background is C/C++ system programming.

I have a main Window with some text fields, buttons, properties etc. I setup outlets and actions (hopefully correctly). Additional window declared in another NIB is loaded upon one of the button clicks:

- (IBAction) openSettings: (id) sender
{
    ConfigurationWindowController * wc=[[ConfigurationWindowController alloc]     initWithWindowNibName:@"Configuration"];

    [wc showWindow:self];
 }

New window is being loaded and shows up.

I need to do following things : 1) pass some string params to the second ("child") window 2) receive this params back to the main window when second window is closing.

I'm not sure what is a correct way to do this in Cocoa.

@sergio : Many thanks for your response! In my "child" window I store pointer to the main window nad before opening child window I pass some params:

ConfigurationWindowController * wc=[[ConfigurationWindowController alloc]     initWithWindowNibName:@"Configuration"];
mConfigWindow = wc;

[mConfigWindow setValuesToURL:@"some string here" storageParam:@"another string"     callerWindowPtr:self];
[wc showWindow:self];

This method is successfully called I see values stored in the "child" window class instance properties. However when I try to assign this values to the textfileds in the setValuesToURL method GUI elements are still null , I tried to assign stored strings in awakeFromNib method but here these properties are null! . Also value of self pointer is different - that means object created initWithWindowNibName and actual window with GUI are different. Obviously stored pointer to the "Main" window also is null when I try to pass back values. I suspect that problem is in NIB setup - really confusing to me. I suspect is common misunderstanding of code/NIB relations, I tried different things but still cant get it work. Any guidance would be really useful.

-(void) setValuesToURL:(NSString*)strServiceURL  storageParam:(NSString*) strStorageURL     callerWindowPtr:(AppletAppDelegate *)_callerWindow
 {
     @try {
          NSLog(@"setValuesToURL was called with params %@ , %@" , strServiceURL     , strStorageURL);
        self.strDataStorageURL = strStorageURL;   
self.strServerURL = strServiceURL;
        self.callerWindow = _callerWindow;
[textServerURL setStringValue:[self strServerURL]];
    [textDataStorageURL setStringValue:[self strDataStorageURL] ];

        NSLog(@" after assigmnemnt  %@ , %@" , [self strDataStorageURL], [self      strServerURL]);

    }
     @catch (NSException * e) {
         NSLog(@"exception inf0 %@  " ,[[ e userInfo]      descriptionInStringsFileFormat]);
    }
    @finally {

    }

}

Good news - now string values are assigned to the NSTextField objects. I have a button on "child" window and on click I'm trying to call back parent pointer window methid :

- (IBAction) saveConfigurationSetings: (id) sender
{
    NSLog(@"saveConfigurationSetings: (id) sender");
        //close window and pass back URL strings 
    self.strServerURL =  [textServerURL stringValue]; 
    self.strDataStorageURL = [textDataStorageURL stringValue];
    [self.callerWindow passMeBackData: [textServerURL stringValue] strStorageURLParam:    [textDataStorageURL stringValue]];

    [self close];

}

Here callerWindow variable is null and passMeBackData fails . Here is declaration in h :

@interface ConfigurationWindowController : NSWindowController {
...
AppletAppDelegate *callerWindow; 
...
}


@property (assign) AppletAppDelegate * callerWindow;

in m file

@synthesize callerWindow;

Williham Totland Williham Totland · Accepted Answer · 2011-05-16T11:48:14

The problem with your approach isn't really how to do that; rather, it's how you've set up your setup.

A more appropriate flow for Objective-C/Cocoa would probably be to do the following:

Add the ConfigurationWindowController to MainMenu.xib; wire it to the menu item ApplicationMenu > Preferences (if memory serves, this should be possible to accomplish simply by implementing - (IBAction)openPreferences:(id)sender, or something to that effect.)
Let the user change the settings, and write them to NSUserDefaults as they go. There's probably no need for a modal window or Apply/Cancel/OK buttons unless your settings are extremely complex or changing them is terribly expensive (computationally).
Either whenever a setting is changed, or the window closes, fire notifications to the application NSNotificationCenter that interested parties can observe. Note: Not all settings require notifications to be fired; only those that affect ongoing processes that cache the value of the setting.

There are other approaches as well, but this is probably the most easily extensible.

If the issue is that of opening the settings window on a specific pane; set the tag value of each control or menu item that opens the window appropriately; and check what pane you should open using [sender tag].

If the issue is that you have an entire extremely specific settings window for each process in your application, that is probably a Bad Thing™.

Cocoa, Objective- C how correctly pass params from one window to another

1 Answers