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Re: help with DUIM application

On Wed, 14 Jun 2000 09:45:01 -0400 (EDT), johncwhi@my-deja.com wrote:

> Now how this fits into the suggestions given already...   Is the
> call-in-frame method the equivalent of the Notify() method?  I'll have
> to think about that some more.

Loosely coupling the components like this is orthogonal to the issue of
combining the threading. It might be done as follows:

8<----------------------------------------------------------------------

begin
  let frame = make(<my-frame>);
  add!(*hooks*, method (data) call-in-frame(frame, update-my-frame, data) end);
  make(<thread>, function: start-data-capture);
  start-frame(frame); // NB uses up main thread
end;

define constant *hooks* = make(<stretchy-vector>);

define method start-data-capture ()
  while (#t)
    let data = blocking-read-for-device-data();
    do(method (hook) hook(data) end, *hooks*);
  end;
end method;

define method update-my-frame (frame :: <my-frame>, data)
  // insert display changing code here
  // (gets run on frame thread)
end method;

8<----------------------------------------------------------------------

Now anyone can add themselves to hooks to get told about new data.

The 'Pattern' literation generally assumes message-passing OO-style. Hence they
are forced to think in terms of protocols (eg Notify), which aren't necessary
in Dylan although you could define them if you wanted to:

8<----------------------------------------------------------------------

begin
  let frame = make(<my-frame>);
  add!(*observers*, frame);
  make(<thread>, function: start-data-capture);
  start-frame(frame); // NB uses up main thread
end;

define constant *observers* = make(<stretchy-vector>);

define method start-data-capture ()
  while (#t)
    let data = blocking-read-for-device-data();
    do(method (observer) notify(observer, data) end, *observers*);
  end;
end method;

define method notify (frame :: <my-frame>, data)
  method (data) call-in-frame(frame, update-my-frame, data) end);
end method;

define method update-my-frame (frame :: <my-frame>, data)
  // insert display changing code here
  // (gets run on frame thread)
end method;

8<----------------------------------------------------------------------

__Jason


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