mfox@hpbsla.HP.COM (Martin_Fox) (11/11/88)
What IS the MVC paradigm? Model and View I can handle, but I never
really understood the use of the Controller.
Long ago, when I was programming in SmallTalk, I noticed some classes
known as "pluggable" views which allowed very easy creation of views.
If I remember correctly, you created a pluggable view and provided it
with the following information:
1) the model object
2) the message selector to send to the model to query for
information to be displayed
3) the message selector to send to the model when an input
event occurred.
For example, a view which allowed a scrollable list of strings to be
displayed and allowed the user to choose an item in the list might
require message selectors for asking the model for the list of items
(strings) and notifying the model when a new item was selected. (Of
course, this over-simplified. There were multiple input and output
events). The view was a dependent of the model; whenever the model
was changed, it had to notify its dependents and the view automatically
queried for the updated information.
This whole scheme relieved the programmer from having to worry about
mouse events, scrolling the display, etc. Is this what the Controller
was for? If so, I didn't miss it. Pluggable views seemed much cleaner,
providing a more abstract layer above the MVC paradigm. For those of
you (yes, you) who have worked with both the MVC and the pluggable views,
which did you prefer? Or do I not know what I am talking about?
Martin Fox
HP Boise Division