Saturday, 4 July 2009

The missing part in Gorm Manual on GNUstep, about 'NewClass' controller

8 Creating an Application
If you have ProjectCenter, you need to open it and create an “Application” project.
Create it with the name “FirstApp”. From there you can open the MainMenu.gorm by
clicking on interfaces and selecting MainMenu.gorm. If is properly installed, you
Gorm should start up.
If you don’t have ProjectCenter, you can create the Gorm file by hand. First you need
to start Gorm. You can either do this by doing ‘gopen’ from a command line
prompt, or you can invoke it from the Dock or from the workspace’s file viewer.
You then need to select the ‘Document’ menu, and then ‘New Application’. This should
produce a new document window, with a menu and an empty window. This should be
the same as with the ProjectCenter gorm file since this is the basic starting point for an
For the sections below... only do one or the other, not both.
8.1 Creating A Class In Gorm
There are two ways to do this next operation. I will take you through each step by step.
First click on the classes icon in the toolbar on the top of the Gorm document window.
You should see the view below change to an outline view containing a list of class names.
Once this happens we’re ready to create a class. Select the class you wish to subclass in
the outline view. For our example we will use the simplest: NSObject. Select it by clicking
on the class name once. Then go to the Classes menu in the main menu and select Create
Subclass (you can also type Alt-Shift-c, which will do this as well. The new class will be
created in the list with the name “NewClass”.
8.2 Using The Outline View
From here double click on the subclass name to make it editable. Type the name of the
class and hit enter. For our example, please use the class name MyController. When you
hit enter an alert panel will appear and warn you about breaking connections, simply select
OK and continue.
This method of inputting the classes was inspired by IB in OPENSTEP 4.2/Mach which
had functionality very similar to this. For users of that the transition to Gorm will be
8.2.1 Adding Outlets In The Outline View
Too add an outlet, select the round icon with the two horizontal lines in it (it sort of looks
like a wall outlet. This should become depressed. Here you need to go to the Gorm Menu,
under Classes select “Add Outlet/Action”. Each time you press this menu item another
outlet will be added with a name similar to newOutlet, as you add more the number at the
end will increase. For now add only one outlet.
To rename the outlet simply double click it and change it’s name like you did the class
above to “value” for the sake of our example.
Chapter 8: Creating an Application 20
8.2.2 Adding Actions In the Outline View
The procedure to add on action is precisely the same as adding an outlet, except you
must click on the button which looks like a target (a circle with a + inside). Add an action
and name it “buttonPressed:” for the sake of our example.
8.3 Using The Class Edit Inspector
This way is much more inline with the “OPENSTEP/GNUstep” philosophy. For each
object there is an inspector, even for Class objects.
Once you have created the class as described in the previous section “Creating a Class
In Gorm”, you must skip to this section to use the inspector. In the Gorm main menu
select Tools and then select “Inspectors”. This will make certain that the inspectors win-
dow is being displayed. Once the inspectors window is up move the pulldown on the top
to “Attributes” and select the class you created which should, at this point, have the name
“NewClass”. You’ll notice that the “Class” field at the top which shows the name’s back-
ground color has turned white, instead of grey. This indicates that this class name is
editable. Erase “NewClass” from the text field and type “MyController”.
8.3.1 Adding Outlets In The Inspector
Adding outlets is very intuitive in the inspector. Simply select the “Outlets” tab in the
tab view and click “Add” to add more outlets, and “Remove” to remove them. For the sake
of our example, add one outlet and name it “value”.
8.3.2 Adding Actions In the Inspector
Very much like above only with the “Actions” tab, add an action called button pressed.
8.4 Instantiating The Class
In the Classes outline view select the new class you’ve created, now called MyController
and then go to the Gorm menu and select Classes, and then Instantiate. The document
window should shift from the classes view to the objects view. Amoung the set of objects
should be a new object called MyController.
8.5 Adding Controls from the Palette
Go to the Gorm menu and select Tools, then Palettes. This will bring the palette window
to the front. The second palette from the left is the “ControlsPalette”. Select that one and
find the button object (it should have the word “Button” in it). Drag that to the window
and drop it anywhere you like.
Repeat this operation with the text field. It’s the control with “Text” in it. We are now
ready to start making connections between different objects in the document.
Chapter 8: Creating an Application 21
8.5.1 Making Connections
The type of application we are creating is known as a “NSApplication delegate” this
means that the MyController object will be set as the delegate of NSApplication.
To make this connection click on NSOwner and hold down the Control button, keep it
pressed as you drag from the NSOwner object to the MyController object. The inspectors
window should change to the Connections inspector and should show two outlets “delegate”
and “menu”. Select the “delegate”, at this point you should see a green S and a purple T
on the NSOwner and MyController objects respectively, and press the “Connect” button
in the inspector. In the “Connections” section of the inspector you should see an entry
which looks similar to “delegate (MyController)” this indicates that the connection has
been made.
Now we need to make connections from the controller to the textfield and from the
controller to the button. Select the MyController object and Control-Drag (as before)
from the object to the text field, this will make an outlet connection. You should see the
connections inspector again, this time select the “value” outlet and hit Connect.
Next, control-drag from the button to the controller, this will make an action connec-
tion. The connections inspector should again appear. This time you need to select the
“target” outlet, to get the list of actions. The list should have only one entry, which is
“buttonPressed:” since this is the one we added earlier. Press Connect. You should see an
entry like “buttonPressed: (MyController” in the Connections section of the inspector.
It is also possible to make this connection to NSFirst, but to keep things simple, make
it directly to the object. If you make the connection to buttonPressed: on NSFirst the
functionality of the application will be unchanged, but the invocation will take the path
described above in the section which describes “The Responder Chain”.
8.6 Saving the gorm file
At this point you must save the .gorm file. Go to the Gorm menu and click Documents
and then select “Save”. If the document was opened from a pre-existing .gorm, it will save
to that same file name. If it is an UNTITLED .gorm file a file dialog will appear and you
will need to select the directory where you want to store the .gorm file and type the name
of the .gorm file.
8.7 Generating .h and .m files from the class.
This is different than saving, some people have gotten this confused with the idea of
Gorm generating the code for the gui. Gorm does nothing of the sort (grin).
Go to the Classes section in the Document window and select the MyController class yet
again. Now go to the Gorm menu and select Classes and the select “Create Class Files”.
This will bring up a file panel and it allow you to select the directory in which to put the
files. It will first create the MyController.m file and then the MyController.h file. Simply
select the directory in which your app will reside and hit okay for both. You can change
the names, but the default ones, which are based on the class name, should be sufficient.

When you look at the .m for this class, you should see the ‘buttonPressed:’ method with
the commecnt ‘/* insert your code here */’ in it. Delete this comment and add ‘[value
setStringValue: @‘‘Hello’’];’. The class should look like this after you’re done:
/* All Rights reserved */
#include "MyController.h"
@implementation MyController
- (void) buttonPressed: (id)sender
[value setStringValue: @”Hello”];
You recall, we connected the textfield to the “value” variable. The call above causes the
method setStringValue to be invoked on the textfield you added to the window.
Also, note that the name of the method is “buttonPressed:”. This is the action which is
bound to the button. When it is pressed the text in the textfield should change to “Hello”.
You now need to build the application either by copying in a GNUmakefile and making
the appropriate changes or by using ProjectCenter’s build capability, depending on if you
use it or not.
This app is available as “SimpleApp” in the Examples directory under the Documen-
tation directory distributed with Gorm. Hopefully this has helped to demonstrate, albeit
on a small scale, the capabilities of Gorm. In later chapters we will cover more advanced
application architectures and topics.

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