trapped

What is trapped?

Trapped is a library for Amber that aims to create bidirectional data-binding UI for Amber. When it is for Amber, how else should it be called than "trapped"?

It is inspired by AngularJS. But it does not aim to be hard port of AngularJS into Amber, it just tries to bring some of the good things, but stay true to Amber/Smalltalk way of doing web UI.

What stage it is in?

Very early. Nevertheless, very basic things are already working. You can try it, though it still misses a lot.

What is working:

• viewmodel -> view update propagation
• showing simple data in view
• iterations in view
• viewmodel -> view change propagation for some tags

What is missing:

• optimizations ;-)
• view -> viewmodel change propagation everywhere

Enhancements for the future:

• better change/update model (implicit, not explicit).

How can I try it?

Easy way (but you cannot save and reload with new code):

Visit http://www.herby.sk/trapped/demo.html.

Hard way (but you can save and reload with new code):

Clone this repo, with submodules as well (amber is bundled as submodule). Then start the server: node vendor/amber/server/server.js. It start on port 4000. Visit http://localhost:4000/demo.html in your browser. Amber IDE opens.

Play with it:

The Todo example from AngularJS is ported into the demo page.

Trapped itself is in Trapped-Frontend and Trapped-Backend packages. The demo page itself is in demo.html and its code is in Trapped-Demo package, in classes App (which is wrapping AppModel) and AppView.

App is the view model entity (its instance is put into global variable AppEntity in demo.html), that is, facade and wrapper around the real object, and AppView is the view. AppModel is plain Smalltalk class holding data and having some behaviour. Instance of this class is wrapped by App.

The entity wraps any object (via model:, as seen in App >> initialize). The view is subclass of plain Widget, but inside it, uses of trap: (and others of trap:xxx: family) on TagBrush and path trapDescend: block allows you to bind data from view model. You can also iterate arrays in the model using TagBrush >> trapIter:tag:do:.

To see viewmodel->view update working, try this in Workspace:

AppEntity modify: #(#todos) do: [ :old | old, { #{'text'->'try the guts'. 'done'->true} } ]

The number and list of items should update. If you do

AppEntity modify: #(#title) do: [ 'My title' ]

The title of the page as well as header should be updated.

The modify:do: should be used for update since it changes as well as signals the change. When using ListKeyedIsolatedEntity subclass as wrapper entity, read:do: and modify:do: guard the data by doing deep copies behind the scene.

If you wish to, you can change the raw data you put into model: by hand, but then be sure to call AppEntity dispatcher changed: #(#title) or similar (you can do AppEntity dispatcher changed: #() to signal everything in AppVM has changed, but then everything depending upon it will redraw).