Another design question

ruby-talk
1

If you remember my previous post titled "automatically call function on
attribute set", you'll remember that I have an airplane class and a
airplane_drawing class, which represents the airplane when drawn on the
screen.

I'm using GTK for this, by the way.

Say the user right clicks on the airplane_drawing object. I want a menu to
popup on the screen with options that when selected will call methods on the
airplane object.

Information on the airplanes is also listed in table form, which reports
each airplane's position, velocity, etc. When I right click on the row that
represents the airplane, I'd like the same popup menu (for now, perhaps it
will be different in the future) to pop up with options that when selected
will call a method on the airplane object.

Question: Since the popup menu has pretty common functionality between the
graphical airplane display and the table airplane display, what would be a
good way to generalize this? Any patterns that would be useful here?

Thanks,
Joe

2

Joe Van Dyk wrote:

If you remember my previous post titled "automatically call function on
attribute set", you'll remember that I have an airplane class and a
airplane_drawing class, which represents the airplane when drawn on the
screen.

I'm using GTK for this, by the way.

Say the user right clicks on the airplane_drawing object. I want a menu to
popup on the screen with options that when selected will call methods on the
airplane object.

Information on the airplanes is also listed in table form, which reports
each airplane's position, velocity, etc. When I right click on the row that
represents the airplane, I'd like the same popup menu (for now, perhaps it
will be different in the future) to pop up with options that when selected
will call a method on the airplane object.

Question: Since the popup menu has pretty common functionality between the
graphical airplane display and the table airplane display, what would be a
good way to generalize this? Any patterns that would be useful here?

For now you say you want the same pop-up menu (meaning same functionality?). If this is the case, make a Singleton class that represents your popup window and it's functionality.

If your airplane_drawing and your table will utilize *most* of the same functionality then still use a Singleton, and allow it to be passed parameters which act as switches. These switches could depict what functionality shows up.

Conceptually speaking maybe something like:

#singleton
class AirplanePopupMenu
    @instance

    #constants
    AP_VELOCITY = 1
    AP_LOCATION = 2
    AP_SIZE = 3
    AP_FUEL = 4
    AP_WEIGHT = 5
    #etc...

    def get_instance
       @instance
    end

    def show_menu( *args )
       #Loop through arrat args which should correspond to the AP_xxx constants we specified
       # above. Depending on the switch then build the rest of your popup menu before displaying it
       # This way users of the AirpanPopupMenu could only utilize the functionality they want
    end

end

Hope I didn't muddy the waters...

Zach

3

Zach Dennis wrote:

Joe Van Dyk wrote:

If you remember my previous post titled "automatically
call function on attribute set", you'll remember that I
have an airplane class and a airplane_drawing class,
which represents the airplane when drawn on the screen.

I'm using GTK for this, by the way.

Say the user right clicks on the airplane_drawing
object. I want a menu to popup on the screen with
options that when selected will call methods on the
airplane object.

Information on the airplanes is also listed in table
form, which reports each airplane's position, velocity,
etc. When I right click on the row that represents the
airplane, I'd like the same popup menu (for now, perhaps
it will be different in the future) to pop up with
options that when selected will call a method on the
airplane object.

Question: Since the popup menu has pretty common
functionality between the graphical airplane display and
the table airplane display, what would be a good way to
generalize this? Any patterns that would be useful
here?

For now you say you want the same pop-up menu (meaning
same functionality?). If this is the case, make a
Singleton class that represents your popup window and
it's functionality.

If your airplane_drawing and your table will utilize
*most* of the same functionality then still use a
Singleton, and allow it to be passed parameters which act
as switches. These switches could depict what
functionality shows up.

Conceptually speaking maybe something like:

#singleton
class AirplanePopupMenu
    @instance

    #constants
    AP_VELOCITY = 1
    AP_LOCATION = 2
    AP_SIZE = 3
    AP_FUEL = 4
    AP_WEIGHT = 5
    #etc...

    def get_instance
       @instance
    end

    def show_menu( *args )
       #Loop through arrat args which should correspond
to the AP_xxx constants we specified
       # above. Depending on the switch then build the
rest of your popup menu before displaying it
       # This way users of the AirpanPopupMenu could
only utilize the functionality they want
    end

end

Hope I didn't muddy the waters...

Zach

How would the AirplanePopupMenu object know what Airplane object's method to
use when the user selects an item from the popup menu?

4

Joe Van Dyk wrote:

How would the AirplanePopupMenu object know what Airplane object's method to
use when the user selects an item from the popup menu?

You could couple Airplane and AirplanePopupMenu. This would allow AirplanePopupMenu to know about the methods on the Airplane class. If there are going to be more then one Airplane object at a time, then allow for the AirplaneMenu to be passed an instance of Airplane. For example:

class Airplane
    def current_speed
       return 290 #speed in mph?
    end
end

class AirplanePopupMenu
    AP_SPEED = 11
       def get_menu( airplane, *args )
       args.each{ |arg|
           case arg
             when AP_SPEED
                  #process the code to add a MenuItem for speed here to your menu
                   menu_item = Menuitem.new
                   menu_item.set_label( airplane.speed )
                   @mymenu.add_menu_item( menu_item )
             else
          end
       return @mymenu
    end
end

I do not use GTK and I haven't used Ruby/Tk in a long while so I won't even attempt to have the code make sense like that. I'll leave the transitioning of code up to you.

Zach