Writing a helper that produces bound results?
문제
I have a date/time formatting helper but what it produces does not update when the underlying property changes. This is not a surprise, but does anyone know how to produce bindings in helpers?
I invoke the helper like this...
{{timestamp created_at}}
...and here is the helper itself:
Handlebars.registerHelper('timestamp', function(context, options) {
var formatter = options.hash['format'] ? options.hash['format'] : 'hh:mm a MM-DD-YYYY';
var original_date = Ember.getPath(this, context); // same as this.get(context) ?
var parsed_date = moment(original_date);
var formatted_date = parsed_date.format(formatter);
return new Handlebars.SafeString("<time datetime=" + original_date +">" + formatted_date + "</time>");
});
해결책
It is now possible to create bound Handlebars helpers using a public Ember API.
Handlebars.registerBoundHelper('timestamp', function(date, options) {
var formatter = options.hash['format'] ? options.hash['format'] : 'hh:mm a MM-DD-YYYY';
var parsed_date = moment(date);
var formatted_date = parsed_date.format(formatter);
return new Handlebars.SafeString("<time datetime=" + date +">" + formatted_date + "</time>");
});
The parameter passed to the helper will have already been resolved, and the helper will be called again whenever the path changes.
다른 팁
It is unfortunately more complex than I'd like to create a custom helper with bound content. Here's an example that Peter Wagenet wrote: https://gist.github.com/1563710
I'll be lobbying for this to become easier.
Not sure if this applies to this particular question, but I also created helpers in views and wanted the values to update when data in the Ember.js view changed. The way I solved this problem was to write an observer on the values I wanted changed and used jQuery to update the specific value.
For example (in Coffeescript):
...
attrObserver: Ember.observer(() ->
$("#attrId").text(this.get("attr"))
...