问题
- I have an object with a variable containing a String.
- I have a window containing a LabelMorph/TextMorph (or some other Morph that displays Text?).
How do i bind the LabelMorph/TextMorph to the variable, so that the label updates when the String in the variable changes?
- classic Smalltalk-80 dependent/change/update mechanism?
- Pharo Announcement framework?
- something different??
How would i do this? Which Morph should i use?
回答1:
Depends on what you want to achieve. You might want to take a look at a way to do it with Glamour in a current Moose image. In a workspace, do-it:
GLMBasicExamples new magritte openOn: GLMMagrittePersonExample sampleData
That shows how to work with announcements on save. The earlier examples are a better way to start understanding how to work with Glamour (and because of the way the examplebrowser is build, the Magritte example doesn't update the list when it is nested):
GLMBasicExamples open
That has several other examples that update on change.
回答2:
Simplest is to use an updating String morph:
UpdatingStringMorph on: self selector: #myLabel
This will send #myLabel (or any other message) to self (or any other object) and display it.
回答3:
This is a solution provided by Benjamin Van Ryseghem on the Pharo Mailinglist:
For this kind of situation, my solution is to use a ValueHolder. Instead of storing your string directly in an instance variable, store it into the ValueHolder.
I tried this in a Workspace:
|string label|
string := 'Wait till i change..' asValueHolder.
label := LabelMorph contents: string contents.
string whenChangedDo: [:newValue | label contents: newValue ].
label openInWindow.
[ 5 seconds asDelay wait. string value: 'I changed :)' ] fork.
来源：https://stackoverflow.com/questions/15534305/how-to-bind-a-labelmorph-textmorph-to-a-variable-so-that-the-morph-reflects-chan