I have a custom element
<!-- element template -->
<dom-module id="custom-element">
<template>
<style></style>
<div class="toggle">
<slot id="toggleContent" name="toggle"></slot>
</div>
</template>
<script>...</script>
</dom-module>
<!--usage-->
<custom-element>
<div slot="toggle">I'm the toggle</div>
</custom-element>
In Polymer 1.0, I could get the distributed child node by using
[this.getContentChildren('#toggleContent')\[0\];][1]
which would return <div toggle>I'm the toggle</div>
However in Polymer 2. getContentChildren isn't supported anymore and doing it this way
this.$.toggleContent.assignedNodes({flatten: true}).filter(function(n) {
return (n.nodeType === Node.ELEMENT_NODE);
});
doesn't return me the expected element, <div slot="toggle">I'm the toggle</div>.
How do I get the equivalent result using assignedNodes() in Polymer 2?
Please see following plunker
Thanks.
Use the following code:
this.shadowRoot
.querySelector('#toggleContent')
.assignedNodes({flatten:true})
.filter(n => n.nodeType === Node.ELEMENT_NODE)
But if you have single slot then you can just do:
this.shadowRoot
.querySelector('slot')
.assignedNodes({flatten:true})
.filter(n => n.nodeType === Node.ELEMENT_NODE)
The this.$ hash is created when the shadow DOM is initialized. Nodes
created dynamically are not added to the this.$ hash. So, you have to use this.shadowRoot.querySelector.
Update After the demo provided:
_toggleEl is an array/object and you are comparing it with an element. So, it is returning false always. So, use var equal = elementClicked === this.toggleEl[0] like you did in polymer 1.
Related
Problem: I have an auto binding template in my main index.html page. Inside the template I am using two of my custom elements. One element is the producer of some data and the other one is the consumer of that data. These custom elements expose published/declared properties for each other to use and bind to. I was able to do that in Polymer 0.5 fairly easily (an example shown below). How do I do the same in Polymer 1.0?
How I used to do in Polymer 0.5?
In Polymer 0.5 I used to data bind between published properties of two custom elements using curly brace syntax and then inside it used the auto node finding concept to directly bind to other element's published property. An example shown below,
<template is="auto-binding">
<my-navigation selectedLabel="Home" id="my_navigation"></my-navigation>
<my-scaffold toolbartitle="{{ $.my_navigation.selectedLabel }}" id="my_scaffold"></my-scaffold>
</template>
I tried something similar in Polymer 1.0 as shown in the example below
<template is="dom-bind">
<my-navigation selectedLabel="Home" id="my_navigation"></my-navigation>
<my-scaffold toolbartitle="{{ $.my_navigation.selectedLabel }}" id="my_scaffold"></my-scaffold>
</template>
But it throws an error:-
Uncaught TypeError: Cannot read property '$' of undefined
You can't do $.* bindings inside the template in Polymer 1.0. Instead, either refactor or use computed functions.
In your situation, since selectedLabel and toolbartitle shares the same value, it is much better to simply bind them to the same property.
Also, attribute names that are declaratively passed in (through the element tag) need to be serialized, so selectedLabel becomes selected-label.
<body>
...
<template id="tpl" is="dom-bind">
<my-navigation selected-label="{{myLabel}}" id="my_navigation"></my-navigation>
<my-scaffold toolbartitle="{{myLabel}}" id="my_scaffold"></my-scaffold>
</template>
<script>
...
window.addEventListener("WebComponentsReady", function (e) {
document.querySelector("#tpl").myLabel = "Home";
...
});
...
</script>
</body>
There is probably a better way to do that, but you can try this:
<body>
<template id="app" is="dom-bind">
<my-navigation selectedLabel="Home" id="my_navigation"></my-navigation>
<my-scaffold toolbartitle="{{ selectedLabel }}" id="my_scaffold"></my-scaffold>
</template>
<script>
var app = document.querySelector('#app');
app.addEventListener('template-bound', function () {
console.log('Our app is ready to rock!');
});
window.addEventListener('WebComponentsReady', function () {
document.querySelector('body').removeAttribute('unresolved');
var my-navigation = document.querySelector('my-navigation');
// This will add the variable to the 'app' context (template)
app.selectedLabel = my-navigation.selectedLabel;
});
</script>
</body>
I'm trying to include classes based on parameters of a json, so if I have the property color, the $= makes the trick to pass it as a class attribute (based on the polymer documentation)
<div class$="{{color}}"></div>
The problem is when I'm trying to add that class along an existing set of classes, for instance:
<div class$="avatar {{color}}"></div>
In that case $= doesn't do the trick. Is any way to accomplish this or each time that I add a class conditionally I have to include the rest of the styles through css selectors instead classes? I know in this example maybe the color could just simple go in the style attribute, it is purely an example to illustrate the problem.
Please, note that this is an issue only in Polymer 1.0.
As of Polymer 1.0, string interpolation is not yet supported (it will be soon as mentioned in the roadmap). However, you can also do this with computed bindings. Example
<dom-module>
<template>
<div class$="{{classColor(color)}}"></div>
</template>
</dom-module>
<script>
Polymer({
...
classColor: function(color) {
return 'avatar '+color;
}
});
<script>
Edit:
As of Polymer 1.2, you can use compound binding. So
<div class$="avatar {{color}}"></div>
now works.
Update
As of Polymer 1.2.0, you can now use Compound Bindings to
combine string literals and bindings in a single property binding or text content binding
like so:
<img src$="https://www.example.com/profiles/{{userId}}.jpg">
<span>Name: {{lastname}}, {{firstname}}</span>
and your example
<div class$="avatar {{color}}"></div>
so this is no longer an issue.
The below answer is now only relevant to versions of polymer prior to 1.2
If you are doing this a lot, until this feature becomes available which is hopefully soon you could just define the function in one place as a property of Polymer.Base which has all of it's properties inherited by all polymer elements
//TODO remove this later then polymer has better template and binding features.
// make sure to find all instances of {{join( in polymer templates to fix them
Polymer.Base.join = function() { return [].join.call(arguments, '');}
and then call it like so:
<div class$="{{join('avatar', ' ', color)}}"></div>
then when it is introduced by polymer properly, just remove that one line, and replace
{{join('avatar', color)}}
with
avatar {{color}}
I use this a lot at the moment, not just for combining classes into one, but also things like path names, joining with a '/', and just general text content, so instead I use the first argument as the glue.
Polymer.Base.join = function() {
var glue = arguments[0];
var strings = [].slice.call(arguments, 1);
return [].join.call(strings, glue);
}
or if you can use es6 features like rest arguments
Polymer.base.join = (glue, ...strings) => strings.join(glue);
for doing stuff like
<div class$="{{join(' ', 'avatar', color)}}"></div>
<img src="{{join('/', path, to, image.jpg)}}">
<span>{{join(' ', 'hi', name)}}</span>
of just the basic
Polymer.Base.join = (...args) => args.join('');
<div class$="{{join('avatar', ' ', color)}}"></div>
<template if="[[icon_img_src]]" is="dom-if">
<img class$="{{echo_class(icon_class)}}" src="[[icon_img_src]]">
</template>
<span class$="{{echo_class(icon_class, 'center-center horizontal layout letter')}}" hidden="[[icon_img_src]]">[[icon_text]]</span>
<iron-icon icon="check"></iron-icon>
</div>
</template>
<script>
Polymer({
echo_class: function(class_A, class_Z) {
return class_A + (class_Z ? " " + class_Z : "");
},
I am calling a polymer element within another element. The inner polymer element has a published attribute to which I am binding JSON from the parent polymer. However it is not getting reflected.
<polymer-element name="parent-test" attributes="testData">
<template>
This is Parent test
<child-test testdatachild="{{testData}}"></child-test>
</template>
<script>
Polymer('parent-test', {
testData: [],
ready: function () {
debugger;
this.testData = [1, 2, 3, 4]
}
});
</script>
</polymer-element>
<polymer-element name="child-test" attributes="testDataChild">
<template>
<!--{{testDataChild}}-->
<template repeat="{{test in testDataChild}}">
{{test}}
</template>
</template>
<script>
Polymer('child-test', {
testDataChild: [],
ready: function () {
debugger;
}
});
</script>
</polymer-element>
I am not sure what could be the problem here.
Edit:
Seems like I am not having the actual parentContent at the time of generating the child-polymer-element.
If I assign hardcoded values in ready function for this.parentContent, it doesnt work as well.
If I assign hardcoded values in create function for this parent.Content, it works.
So, I am not not sure if this is something related to generating the child polymer element before the values getting binded to parent.
Thanks,
Sam
I modified your plunk example and get it working without your workaround :
Plunk
<polymer-element name="child-test" attributes="testdatachild">
<template>
<br><br>
In Child el.:
<br>
<template repeat="{{test in testdatachild}}">
{{test}}
<br>
</template>
</template>
<script>
Polymer('child-test', {
ready: function () {
}
});
</script>
This is Parent test
<child-test testdatachild="{{testData}}"></child-test>
<br>
</template>
<script>
Polymer('parent-test', {
created: function () {
this.testData = [1, 2, 3, 4];
}
});
</script>
The main problem seems to be the order of the code
I guess it works better to first declare the child, then the parent, as the child is used in the parent...
Also, as specified in the polymer documentation :
polymer
Important: For properties that are objects or arrays, you should always initialize the properties in the created callback. If you set the default value directly on the prototype (or on the publish object), you may run into unexpected “shared state” across different instances of the same element.
Here is modified example of you code that works : Plunk
Why your example is not working, I don't have all answers buy you are right for one:
<!-- This won't work cause:
"Attributes on child-test were data bound prior to Polymer upgrading the element.
This may result in incorrect binding types." -->
This is Parent test
<child-test testdatachild="{{testData}}"></child-test>
I have a general question. One of the major benefits of building a new polymer element is that it can be used like a native HTML element in a page. So, depending on the element that you build, it's logical that you would be able to add multiple instances of that element in a page.
Say I build a simple task list polymer element that has multiple views. A simple view that just lists the task names in a list and a detailed view that list the tasks and many other properties of the task in a list.
Then I add the element to my page multiple times. Maybe I want one instance of the element to list tasks related to Home and another to list tasks related to Work. But I want to send a link to someone with the Home task list opened in the simple view and the Work task list opened in detailed view. Or maybe I want the Home task list opened in edit mode and the Work task list opened in view mode.
How would you build the element so that you can change attributes/settings to more then one of these elements on a page?
The beauty of polymer is that you can change your component view by just adding / changing attributes to it.
Create custom tags and provide specific attributes depending on your requirement (HOME / WORK profile), and change your view accordingly.
Example:
Step 1: Create task container
<polymer-element name="task-list" noscript>
<template>
<h3>Tasklist</h3>
<core-menu id="tasks">
<content></content>
</core-menu>
</template>
</polymer-element>
Step2: Create task component
<polymer-element name="add-task" attributes="label detail">
<template>
<div id="task">
<input type="checkbox" id="tick" on-click="{{lineThrough}}" /> {{label}}
<div style="color:#999;margin: 5px 25px;">
{{detail}}
</div>
</div>
</template>
<script>
Polymer('add-task', {
lineThrough: function() {
this.$.task.style.textDecoration = this.$.tick.checked ? 'line-through': 'initial';
}
});
</script>
</polymer-element>
And now using above components, you can create your basic task list:
<task-list>
<add-task label="Learn Polymer" detail="http://www.polymer-project.org/"></add-task>
<add-task label="Build something great" detail="create polymer element"></add-task>
</task-list>
Screenshot
Now, To have control over changing task view (list / detailed / editable). Just add 2 attributes to task-list component. To control child view add-task from parent task-list element, you need to publish properties of your child element.
Your child component should be:
<polymer-element name="add-task" attributes="label detail">
<template>
<div id="task">
<template if="{{isEditable}}">
<input value="{{label}}" />
</template>
<template if="{{!isEditable}}">
<input type="checkbox" id="tick" on-click="{{lineThrough}}" /> {{label}}
</template>
<template if="{{isDetailed}}">
<div style="color:#999;margin: 5px 25px;">
{{detail}}
</div>
</template>
</div>
</template>
<script>
Polymer('add-task', {
publish: {
isDetailed: false,
isEditable: false
},
lineThrough: function() {
this.$.task.style.textDecoration = this.$.tick.checked ? 'line-through': 'initial';
}
});
</script>
</polymer-element>
Parent component with required attributes
<polymer-element name="task-list" attributes="editable detailed">
<template>
<h3>Tasklist</h3>
<core-menu flex id="tasks">
<content></content>
</core-menu>
</template>
<script>
Polymer('task-list', {
editable: false,
detailed: false,
domReady: function() {
var items = this.$.tasks.items;
for(var i = 0; i < items.length; i++) {
items[i].isDetailed = this.detailed;
items[i].isEditable = this.editable;
}
}
});
</script>
</polymer-element>
That's it, now you can control your task view by specifying required attributes to your parent component.
<task-list detailed editable>
<add-task label="Learn Polymer" detail="http://www.polymer-project.org/"></add-task>
<add-task label="Build something great" detail="create polymer element"></add-task>
</task-list>
Screenshots
With detailed and editable attributes
Without detailed and editable attributes
This seems a trivial thing but I'm unable to find it:
What if I want to reverse the order of my items in a repeat, without actually touching the order of the array, like in:
<template repeat="{{layer in layers}}">
<div>{{layer.name}}</div>
</template>
where layers is an array of objects.
I've tried applying a filter and then working with a copy of the array, like in:
<template repeat="{{layer in layers | reverse}}">
<div>{{layer.name}}</div>
</template>
...
reverse: function(arr){
return _(arr).reverse();
}
but that results in some observers failing since they're looking at the copy instead of the original objects. I don't want to apply a sort to my original array since other parts of the code depend on that order.
Anyone knows of an option where just the order of display in the DOM is affected?
I think you need to do something like this
<template repeat="{{layer in temp_array}}">
<div>{{layer.name}}</div>
</template>
<script>
Polymer('el-name',{
ready: function(){
this.temp_array =[];
this.temp_array = layers.reverse();
}
}
);
</script>
if your layers is empty when ready called, use change listener
<script>
Polymer('el-name',{
ready: function(){
this.temp_array =[];
},
layersChanged: function(oldValue, newValue){
if(newValue.length != 0)
this.temp_array = newValue.reverse();
}
}
);
</script>
Hope it help for you
If it is possible to put the repeated elements in a vertical/horizontal layout, then reverse might do the trick (see layout documentation):
<div vertical layout reverse?="{{ isReversed }}">
<template repeat="{{ layer in layers }}">
<div>{{ layer.name }}</div>
</template>
</div>
I would like to offer a safier and more clear way to revert an array for repeat binding:
<polymer-element name="my-element" attributes="layers layersReversed">
<template>
<template repeat="{{layer in layers}}">
<div>{{layer.name}}</div>
</template>
</template>
<script>
Polymer({
layersReversedChanged: function() {
var layers = this.layersReversed.slice();
layers.reverse();
this.layers = layers;
}
});
</script>
</polymer-element>
<my-element layers="{{layers}}"><!-- direct order --></my-element>
<my-element layersReversed="{{layers}}"><!-- reverse order --></my-element>
Direct or reverse order is defined by used attribute: layers or layersReversed.
There are no value changing in corresponding -Changed event by itself (which may cause falling to endless loop).
The .reverse() method changes the original array, so it should be applied on its copy.
There is another funny and extravagant way to do the same via an intermediate web-component:
<polymer-element name="reverse-order" attributes="in out">
<template></template>
<script>
Polymer({
inChanged: function() {
var out = this.in.slice();
out.reverse();
this.out = out;
}
});
</script>
</polymer-element>
It can be used to bind some elements with different order. I.e., array is populated by .push() method, while preferred array presentation is in reverse order:
<my-element layers="{{layersReversed}}"></my-element>
<reverse-order in="{{layers}}" out="{{layersReversed}}"></reverse-order>
<core-localstorage name="layers" value="{{layers}}"></core-localstorage>