Hi Gonzalo,
First off, observing the element's *own* properties, like in
`core-drag-drop` is no problem in 1.0. That same observer would look like
this:
observers: [
'coordinatesChanged(x,y)'
],
coordinatesChanged: function(x, y) { ... }
You can also *bind* to a property on a local DOM child:
<dom-module is="test-el">
<template>
<!-- bind child-el.childProp to test-el.parentProp -->
<child-el id="child" child-prop="{{parentProp}}"></child-el>
</template>
<script>Polymer({ ... });</script>
</dom-module>
Now the value of `childProp` is available in your element as `parentProp`
so you can
define an observer for it:
observers: [
'childPropChanged(parentProp)'
]
In 0.5, you could skip the binding and observe a child prop directly, doing
something like:
observe: {
'$.child.childProp': 'childPropChanged'
}
This shortcut is what you can't do anymore. An element can only create
observers for its own properties.
Further reading:
https://www.polymer-project.org/1.0/docs/devguide/properties.html#change-callbacks
https://www.polymer-project.org/1.0/docs/devguide/data-binding.html
Hope that helps,
Arthur
On Wed, May 4, 2016 at 1:40 PM, Gonzalo Tirapegui <
[email protected]> wrote:
> Hi , in your core-drag-drop functions (implemented on polymer 0.5) as you
> can see in this source
> <https://github.com/Polymer/core-drag-drop/blob/master/core-drag-drop.html> ,
> line 35-37 the polymer component (as i understand) observes the x and y
> property of itself and it call to the coordinatesChanged method to execute
> it , when you search in the migration guide you say "Unlike Polymer 0.5,
> observers do not support the this.$.elementId syntax for observing
> changes to the properties of local DOM children. However, in some cases you
> can use data binding to bind a property to the child element’s property,
> and observe the local property instead." , so , how you can observe the
> same property (on Polymer 1.0) if you can't reference it?
>
> Follow Polymer on Google+: plus.google.com/107187849809354688692
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