I have my main element using the flatiron-element to redirect my user:
....
<template if="{{route != null}}">
<template if="{{route == 'home' || route == ''}}">
<home-element structure="{{home}}"></home-element>
</template>
<template if="{{route == 'research'}}">
<research-element structure="{{research}}"></research-element>
</template>
<template if="{{route == 'highlights'}}">
<!-- <highlights-element></highlights-element> -->
</template>
</template>
....
Each time I change {{route}}, the elements get recreated. Is there a good way to cache it so we do not have to reload it if it was previously loaded?
Thanks
What you're seeing is Polymer's template system instantiating each element as needed. When you cycle routes, it adds/removes the element from the DOM. The next time a round, the data-binding system stamps out a new instance of the element. This also means created() and ready() get called "again".
One option is to use <polymer-ui-pages> for this: http://www.polymer-project.org/docs/elements/polymer-ui-elements.html#polymer-ui-pages
Another is to show/hide elements as needed in CSS (instead of using conditional templates): http://jsbin.com/zeyoyisu/2/edit
Related
I'm setting up a contact list in Polymer 1.0. When the user clicks on a name, there should be a (animated) page opened for further details. All of these data elements are pulled from an external .json file.
Two questions for this approach..:
1) where to begin? How do I wrap, for example, an iron-page or neon-animated-page around my current setup (which is searchable, which is also the -temporary- reason it's a dom-repeat instead of an iron-list):
<template id="resultlist" is="dom-repeat" items="{{data}}" filter="contactFilter">
<paper-item>
<paper-item-body two-line>
<div>{{item.name}}</div>
<div secondary>{{item.number}}</div>
</paper-item-body>
</paper-item>
</template>
2) For quick try-out with binding options I've created an paper-dialog (instead of an page behaviour) which displays further data for the chosen person... On top of that paper-dialog should the chosen name being displayed. But I only get the first name of the array in my .json file. How can I setup the code to display the {{item.name}} of the chosen item?
Ps. I'm aware of the contacts-app from Rob Dodson (https://github.com/robdodson/contacts-app), but I can't figure out how it should be done in Polymer 1.0.
Update 27.10.2015
After Hugo's answer I'm not able to get the solution to work in an dom-module structure.
Sorry for misunderstanding, but I can't figure out where I'm wrong.
Having to following:
phonebook.html, which acts like an index
...
<body unresolved>
<template is="dom-bind" id="application">
<neon-animated-pages selected="[[selected]]" entry-animation="fade-in-animation" exit-animation="fade-out-animation">
<contact-list></contact-list>
<contact-details></contact-details>
</neon-animated-pages>
</template>
<script>
var application = document.querySelector('#application');
application.selected = 0;
document.addEventListener('show-details', function() {
application.selected = 1;
});
document.addEventListener('show-list', function() {
application.selected = 0;
});
</script>
</body>
DOM-module contact-list.html, the list it self.
<dom-module id="contact-list">
<template>
<style include="phonebook-styles"></style>
<iron-ajax url="../data/data.json" handle-as="json" last-response="{{data}}" auto></iron-ajax>
<div class="container">
<h3>Contactlist:</h3>
<div class="template-container">
<template is="dom-repeat" id="templateUsers" items="{{data}}">
<paper-item on-tap="showDetails">
<paper-item-body two-line>
<div>{{item.name}}</div>
<div secondary>{{item.phonenumber}}</div>
</paper-item-body>
<div class="item-details-link">
<iron-icon icon="account-circle"></iron-icon>
</div>
</paper-item>
</template>
</div>
</div>
</template>
<script>
Polymer({
is: 'contact-list',
properties: {
selectedContact:{
type:Object,
value:function(){
return null;
}
}
},
showDetails: function(ev) {
var data = this.$.templateUsers.itemForElement(ev.target);
//alert(JSON.stringify(data)) // works with data chosen data selection...
this.selectedContact = data;
this.fire('show-details', this.selectedContact);
}
});
</script>
</dom-module>
DOM-module contact-details.html, the details-list.
<dom-module id="contact-details">
<template>
<!-- Do I need to declare the .json in my details module? -->
<iron-ajax url="../data/data.json" handle-as="json" last-response="{{data}}" auto></iron-ajax>
<paper-icon-button icon="arrow-back" on-tap="showList"></paper-icon-button>
<h3>Contact details</h3>
<template is="dom-repeat" items="{{data}}">
<div>{{selectedContact.name}}</div>
</template>
</template>
<script>
Polymer({
is: 'contact-details',
showList: function() {
this.fire('show-list');
}
});
</script>
</dom-module>
Everything, like the transitions, work. The chosen contact is also displayed in an alertbox (commented out in contact-list.html), but isn't forwarded to the contact-details.html page.
There are multiple steps to implement the solution:
Setup the neon animated pages ( one page would be the contact list, the other page would be the details )
Display the list of contacts ( you already have this one )
Add a "selectedContact" property to your element
Add a tap/click handler to the list items element and inside the handler set the selectedContact. You need to get the contact item from the DOM element clicked. ( Check an example here : http://jsbin.com/lofarabare/6/edit )
You can bind the contact details page elements to the selectedContact properties, e.g {{selectedContact.name}}
Inside the handler also Change the neon animated pages selected property to have it display the animation to the other page.
-- Extra feedback
I checked the way you handle events, feedback below:
Give the elements some id so you can add the event listener directly to them (e.g application.$.myContactList.addEventListener('show-detail',function(ev){...})
The way you fire the event from the contact-list is correct, however you are not reading the event data inside the event listener for the 'show-detail' event. The event listener receives the event as argument "ev". You can get the event data using ev.detail
With the event data (the selected contact) you can update your contact details component. Give it some id like 'details' and just update the 'selectedContact' property. **You need to declare the selectedContact in the details component, right now you don't have it there **
I have a question regarding dom-repeat. I have two different elements like:
<host-element>
<item-element></item-element>
<item-element></item-element>
</host-element>
each item-element has an array, in which items can be added at runtime. When the item-element
is attached is fires an event, so that the host-element knows about the item-element within its content and adds each
item-element to an array of item-elements to a property. To access the item-element
item arrays you could bind to the property of the host-element like:
<host-element items="{{itemElements}}">
<item-element></item-element>
<item-element></item-element>
</host-element>
to print the content of the itemElements iterate over it with dom-repeat
<template is="dom-repeat" items="{{itemElements}}">
<ul>
<template is="dom-repeat" items="{{item.values}}" as="value">
<li>[[value]]</li>
</template>
<ul>
</template>
so far everything works as expected. When the item-element change the dom-repeat
should redraw itself, but it is not happening. The documentation states you could uses dom-repeat.observe or dom-repeat.render
to update the dom-repeat element. Using dom-repeat.render manually works and could be
run automatically, but is not ideal. Therefor I am trying to find a solution with dom-repeat.observe with no luck so far.
<template is="dom-repeat" items="{{itemElements}}" observe="values.splice">
<ul>
<template is="dom-repeat" items="{{item.values}}" as="value" observe="????">
<li>[[value]]</li>
</template>
<ul>
</template>
I have pushed my source to github at source and a live demo
Thanks for your help.
Sandro
I have found a hack to get it to work. I need to alter the array holding all items.
The function _itemElementChanged is called every time a item-element is changed.
_itemElementChanged: function(){
// the check is needed if this function is run multiple times in the same tick it would erase the whole array
if (this.items.length > 0){
var itemsTmp = this.items;
this.items = [];
this.async(function () {
this.self.items = this.items;
}.bind({items: itemsTmp, self: this}));
}
}
The check for of this.items.length > 0 is need incase _itemElementChanged is called twice
before the async function runs. In that case this.items would end up empty.
This is by fare not a satisfying solution, but its the only working on I found so far.. I have updated the source to include the solution.
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 using this template.
<template repeat = "{{cover in covers | keys}}">
<div class ='item'>
<img src="{{cover}}"></img>
</div>
</template>
and in my polymer script
domReady: function () {
//aplly some css
}
but when i debug the repeat is not over when the ready event is fired, so my css style changes is not happening.
It would be best to know what CSS you're trying add. Typically, you should not try to manage the DOM of a <template repeat> yourself. Instead, tweak it with your data model. For example, you could dynamically apply the "show" class to the image based on a property it sets:
<template repeat = "{{cover in covers | keys}}">
<div class ='item'>
<img src="{{cover}}" class="{{ {show: cover.show} | tokenList }}">
</div>
</template>
or do something similar by setting an inline style.
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>