如何在Polymer 1.0中取消绑定属性

Question

In Polymer 1.0 we can bind an element property to a variable:

<paper-textarea id='area' value={{some_variable}}></paper-textarea>

How can I unbind it?

Below is a solution that doesn't works for me. When some_variable changes it updates area value.

this.$.area.value = "foo";

Answer 1

You can't dynamically bind and/or unbind to element attributes in Polymer 1.0, because bindings are baked during element registration time, not during created/ready/attached. Ref Binding imperatively

Honestly I'm not exactly sure what your use-case is; however, it highly likely that you can achieve it by a) binding your value attribute to a computed function ; or b) bind to a dummy variable

<paper-textarea id='area' value={{letsCompute(some_variable)}}></paper-textarea>

...

letsCompute: function (v) {
  //return your logic to bind or unbind
},
...

Answer 2

It is not 100% clear what you are trying to achieve, but with Polymer you can do one-way data binding.

Downward binding:

<script>
  Polymer({
    is: 'custom-element',
    properties: {
      prop: String    // no notify:true!
    }
  });

</script>

...

<!-- changes to "value" propagate downward to "prop" on child -->
<!-- changes to "prop" are not notified to host due to notify:falsey -->
<custom-element prop="{{value}}"></custom-element>

Upwards binding:

<script>
  Polymer({
    is: 'custom-element',
    properties: {
      prop: {
          type: String,
          notify: true,
          readOnly: true
        }
    }
  });
</script>

...

<!-- changes to "value" are ignored by child due to readOnly:true -->
<!-- changes to "prop" propagate upward to "value" on host  -->
<custom-element prop="{{value}}"></custom-element>

Check out the documentation for more information.