[squeak-dev] The Inbox: Monticello-ct.712.mcz

Jakob Reschke forums.jakob at resfarm.de
Wed Jan 15 20:39:33 UTC 2020

Since you mentioned the #future, I recently tried to wrap modal dialog
(well not really, it is not exclusive, it just has a synchronous API to
obtain the result) with a promise interface and came up with the following.
If I thought it through correctly, it should not lose the continuation even
when the UI process is terminated and replaced (via Ctrl+., abandon, for
example). Haven't tested it yet, though. Would anyone like to review?

In the model...
selectedChangesWithTitle: titleString
| builder |
builder := ToolBuilder default.
view := builder open: self label: titleString.
promise ifNil: [promise := Promise new].
self future resumeModalRequest. "will resolve the promise"
^ promise

view ifNil: [self error: 'Tool was not opened yet'].
promise ifNil: [self error: 'Tool was not opened with
[ToolBuilder default runModal: view]
["Make sure we will notice in a new UI process when the view is closed."
self future resumeModalRequest].
"If we finally get here, the view was closed."
self accepted ifTrue: [promise resolve] ifFalse: [promise reject].

Am Mi., 15. Jan. 2020 um 21:32 Uhr schrieb Jakob Reschke <
forums.jakob at resfarm.de>:

> Am Mi., 15. Jan. 2020 um 09:13 Uhr schrieb Thiede, Christoph <
> Christoph.Thiede at student.hpi.uni-potsdam.de>:
>> You proposed using a promise - I never had the pleasure to meet them
>> until today. Maybe you have a minimum working example for demonstrating
>> your proposal? FutureNodes seem to be used very rarely in Trunk :-)
> I have no minimum example ready, but here is the outline:
> - Add an instance variable for the promise to the model.
> - Initialize with `Promise new` when the model is asked to open a view.
> - Answer the promise to the open message.
> - In the model's method that is invoked when the dialog is accepted,
> promise resolveWith: theResultOfWhatHappened
> - In the method that opens the tool, take the promise and use
> whenResolved:, whenRejected: (handle the outcome) or then:ifRejected:
> (handle the outcome and answer another promise -- chaining). Do not attempt
> to return from the handler blocks, the method will have returned by the
> time they are evaluated.
> Of course it is a totally different style of programming than with modal
> windows.
> Similar alternative without promises:
> - Instead of a promise, store a MessageSend in the model.
> - In the client of the model, store all necessary state to continue in
> instance variables.
> - Do not expect a return value from opening the view for the model.
> - Have the model send the message to self upon continuation.
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