Create a new Cocoa Application project in Project Builder (File → New Project → Application → Cocoa Application) named “Simple Inspector”, and save it in your ~/LearningCocoa folder.

Open the MainMenu.nib file in Interface Builder.

Create a subclass of NSObject in Interface Builder, named Controller. (Click on the Classes tab of the MainMenu.nib window, find NSObject, Control-click it, and select Subclass NSObject).

Create an action method on the Controller class, named showInfoPanel:.

Create four outlets on the Controller class, named infoPanel, infoPanelController, textLengthField, and textView, and assign their types as shown in Table 16-1 and Figure 16-2.

infoPanel

NSPanel

infoPanelController

NSWindowController

textLengthField

NSTextField

textView

NSTextView

Figure 16-2. Creating outlets on the Controller class

The infoPanel outlet will hold a reference to our inspector panel. The infoPanelController will serve as the window controller for the panel. The textFieldLength outlet will point to a text field in our inspector panel that will display the total number of characters in the textView.

Generate the source-code files for the Controller class (Classes → Create Files for Controller).

Instantiate the Controller class (Classes → Instantiate Controller).

Drag a text view out to the application’s main window, and set its Autosizing attributes so that it will resize along with the window that contains it.

Control-drag a connection from the Controller instance object to the text view, as shown in Figure 16-3, and connect it to the textView outlet.

Figure 16-3. Connecting the text view to the Controller

Add a Show Info menu item to the MainMenu’s Window menu, as shown in Figure 16-4. Give it a key equivalent of

-I. This will let the user of our application get the info panel either by using the menu item or by just using the Command-key equivalent.

From the Cocoa-Menus palette:

Figure 16-4. Adding a Show Info window to the application’s menu bar

Connect the Show Info menu item to the Controller’s showInfoPanel: action method by Control-dragging a connection from the menu item to the Controller object, as shown in Figure 16-5.

Figure 16-5. Connecting the menu item to the showInfoPanel: action method

Save (

-S) and close (

-W) the nib file.

Create a new nib file in Interface Builder (File → New). Interface builder will show a dialog box similar to that in Figure 16-6. Select Empty and click New.

Figure 16-6. Interface Builder’s starting point

Save the file as InfoPanel.nib in your ~/LearningCocoa/Simple Inspector /English.lproj folder, as shown in Figure 16-7. You will be prompted to add the nib file to the Simple Inspector target; click the Add button to do so.

Figure 16-7. Saving the InfoPanel.nib file

Now, we need to designate our Controller class as the object that will be the File’s Owner for this nib file at runtime. To let Interface Builder know that the Controller class exists, drag the Controller.h file from Project Builder onto the InfoPanel.nib window.

Select the File’s Owner proxy object in the InfoPanel.nib window, and, using the File’s Owner Info inspector as shown in Figure 16-8, set the File’s Owner class to Controller.

Figure 16-8. Setting the File’s Owner class

This tells Interface Builder that the class responsible for loading this nib file will be of type Controller. By setting this class as the File’s Owner, we can designate that various interface components in this nib file should be connected to the outlets of the Controller class.

Drag out a panel from the Windows palette. Name the panel Info by using the NSPanel Info inspector, as shown in Figure 16-9. Also, make sure that the Hide on deactivate and Utility window (Panel only) options are checked. These options will make our panel look like an Info panel and ensure that it disappears when our application is not active.

Figure 16-9. Creating the Info panel

Drag two text fields onto the panel; name them “Length of Text View:” and “Number”. Control-drag a connection from the File’s Owner proxy object (remember, this is a stand-in for our Controller class) to the Number field, and set the textLengthField outlet, as shown in Figure 16-10.

Figure 16-10. Connecting the textLengthField

Control-drag a connection from the File’s Owner object to the Panel object in the InfoPanel.nib window, as shown in Figure 16-11, and connect it to the infoPanel outlet.

Figure 16-11. Connecting the infoPanel outlet

Save the nib file (

-S), and return to Project Builder.

Edit the Controller.m file as follows:

#import "Controller.h"

@implementation Controller

- (IBAction)showInfoPanel:(id)sender
{
    if (!infoPanelController) {                                        // a
                                [NSBundle loadNibNamed:@"InfoPanel" owner:self];               // b
                                infoPanelController = [[NSWindowController alloc]              // c
                                    initWithWindow:infoPanel];
                            }
                            [textLengthField setIntValue:[[textView textStorage] length]];     // d
                            [infoPanelController showWindow:self];                             // e
}

@end

The code we added performs the following tasks:

Build and run (

-R) the application. Enter some text into the text view, then show the Info panel (Window → Show Info or

-I). You should see something like Figure 16-12.

Figure 16-12. Our inspector in action

Add the following code to the Controller.m file:

#import "Controller.h"

@implementation Controller
- (void)awakeFromNib                                                      // a
                        {
                            NSNotificationCenter * center = [NSNotificationCenter defaultCenter];  
                            [center addObserver:self                                               
                                       selector:@selector(textDidChange:)
                                           name:NSTextDidChangeNotification
                                         object:textView];
                        }

                        - (void)textDidChange:(NSNotification *)notification                   // b
                        {
                            [textLengthField setIntValue:[[textView textStorage] length]];         
                        }

- (IBAction)showInfoPanel:(id)sender
{
    if (!infoPanelController) {
        [NSBundle loadNibNamed:@"InfoPanel" owner:self];
        infoPanelController = [[NSWindowController alloc] 
            initWithWindow:infoPanel];
    }
    [textLengthField setIntValue:[[textView textStorage] length]];
    [infoPanelController showWindow:self];
}

@end

The code we added performs the following tasks:

Build and run (

-R) the application. Show the Info panel (Window → Show Info or

-I), then type text into the text view. The info panel will now keep up with the correct number of characters in the text view as you type.