I am working on a dashboard, in which I have a search panel at the top (let's call it component A), where users can enter a query. The value of this input will change a lot of other components in the dashboard (not only components that are its direct descendants or siblings). I want to send the search value from component A to component B, which should then respond by performing some action with the input value.
I have tried a few things:
Directly calling the function in component B. Haven't been able to get that to work at all.
Manually setting B's local property value and using an observer to trigger a function call. I manager to set the value, but the observer does not trigger.
Using a global variable, which I can easily access across components, but I still can't trigger functions in specific components.
How can I best do this?
I'm relatively new to Polymer, so forgive me if my ideas aren't completely 'Polymerised' :)
Approach 1
<dom-module id="component-B">
<template>
</template>
<script>
Polymer({
is: 'component-B',
properties: {
id: '',
observer: '_idUpdate'
},
_idUpdate: function(){
console.log("HELLO");
}
});
</script>
</dom-module>
<dom-module id="component-A">
<template>
</template>
<script>
Polymer({
is: 'component-A',
idSearch: function() {
var id = this.$.search.value;
document.querySelector('component-B').properties.id = id;
},
});
</script>
</dom-module>
As you want to send data to multiple elements (which might not be siblings of the firing element) you can use any of these two methods
Use iron-signal to fire the signal and then in all the elements where you want the data use iron-signal tag to listen to the signal
<iron-signals on-iron-signal-<signal-name>="<function>"></iron-signals>
You can also use standard HTML method dispatchEvent to fire a signal and then add eventListeners in all the element where you want data.
Related
I'm wondering, is there a possibility to have databindings "out of" a template? Say I have a <template/>-Tag somewhere which I put into the slot of a different component - that component stamps it to its context. Then I want to bind data from the root element to the <template/>-Tag. Also, event bindings (on-x-changed) don't work, because you can't assign a function which is defined in the hosting component. Any ideas?
Example:
... host
{{boundData}}
<binding-component>
<template>
{{boundData}}
</template>
</binding-component>
I don't see changes when I observe boundData in the hosting component. Is there a way to get around this? Or is firing a custom event my only chance?
If you are looking for binding a property outside of polymer something like from index.html you may bind value with element. an example ; index.html
<dom-bind>
<template>
<binding-component bound-data="{{boundData}}"></binding-component>
</template>
</dom-bind>
<script>
// set a value a string, Number or Object etc.
// Optionally wrap this code into a listener ie;
// window.addEventListener('load', e=> { ...below code ... })
var boundData= document.querySelector('dom-bind');
boundData = {} //
</script>
Now in your binding-component element has a property as boundData
hope its helps or provide more code to understand better.
I've made it work the way dom-if does it, too. Like in dom-if (reference), I'm creating a Templatize-instance which then uses forwardHostProp to handle the "inside"-properties
this.__ctor = Templatize.templatize(template, this, {
mutableData: true,
forwardHostProp(prop, value) {
// handling item updates, item being the only property
// from within the binding component
// everything else is automatically bound by templatize
this.set(prop, value);
this.update(this.item);
},
});
this.__instance = new this.__ctor();
this.root.appendChild(this.__instance.root);
This all happens in connectedCallback.
Because the Templatize-instance is passed this, it's bound to the current context as well.
Good luck!
I'm building a new webapp and I need to know how can I pass an object between 2 custom elements in polymer.
In the code below, I set the value of mydata in "my-child-element-1" and I need to see this value in "my-child-element-2"...I think that it's not very hard to do but i'm loosing my mind to find a good solution...
In my opinion, i should create a temporary object in "my-host-element" to share the value but i'm not convinced about this...
This is my code:
<dom-module id="my-host-element">
<template>
<my-child-element-1 mydata="{{mydata}}"></my-child-element-1>
<my-child-element-2 mydata="{{mydata}}"></my-child-element-2>
</template>
<script>
Polymer({
is: "my-host-element",
properties:
{
mydata: {
type: Object
}
}
});
</script>
</dom-module>
Thank you!!
Your example looks like it should work without the host element needing a property, if the property on the child elements are set up correctly. Remember that Polymer's data binding syntax is basically syntactic sugar around firing and handling custom events. So take a look in child element 1 and make sure that you've set the property to notify when changed. For example:
Polymer({
is: "my-child-element-1",
properties: {
mydata: {
type: Object,
notify: true // fire mydata-change CustomEvent on change
}
}
});
Yes, afaik it is correct to have the parent element act as the mediator between the children, which means it needs to have its own property even if its only used for that purpose.
This question had been modified to match the actual problem.
The original question mistakingly focused on iron-ajax, please see the original problem below. The question should have been:
Please advice why child iron-ajax element is not ready during the 'ready' callback of my-component defined as follows:
<dom-module id="my-component">
<template>
<link rel="import" href="../../../bower_components/iron-ajax/iron-ajax.html">
<iron-ajax
id="selectionLoader"
url=""
method="GET"
handle-as="json"
debounce-duration="300"
last-response="{{ suggestedOptions }}"
last-error="{{ lastError }}"
verbose=true
>
</iron-ajax>
</template>
</dom-module>
<script>
(function () {
Polymer({
is : 'paper-select',
ready : function() {
console.log(this.$.selectionLoader.generateRequest); // undefined
}
})
})()
</script>
Original question
Original title: 'WebComponentsReady' fires before iron-ajax ready - Polymer 1.0
I need to assign some values to an observed property of a custom component that internally uses iron-ajax with disabled auto - so I need to call .generateRequest on the iron-ajax element. This should happen when host page/component is ready, in order to fetch from the server some defaults based on data in the host component code.
selected is an array property on the component observed like this:
observers: [
'_selectedChanged(selected.splices)' // _selectedChanged calls .generateRequest
]
The observer is triggered by:
window.addEventListener('WebComponentsReady', function() {
document.querySelector('paper-select').selected = [{id : 11855},{id : 11856}];
});
The problem is that WebComponentsReady fires before .generateRequest is available on the iron-ajax. So my component is initialized, _selectedChanged is called, but iron-ajax inside it is missing the method and in fact other properties/methods as well.
I've implemented a "deferred" workaround using setTimeout inside the component and it works like charm but it's obviously not the way. Also everything works if the observer is triggered some time later after the page load, e.g. by user's typing. This shows that the logic works, it's just the timing that is wrong.
What am I missing?
The real issue was having the html imports inside my component's <template>.
The 'wrong' order of events makes sense as iron-ajax is not even registered at the time when its host calls the 'ready' callback.
I've moved the imports outside <dom-module> and now everything works as expected.
A flux architecture is trending in web applications and so is polymer elements.
Is there any example how to make a polymer application, which use flux architecture?
I've been thinking about using the Flux pattern with (Polymer) Web Components. Up to date I have come up with three possible solutions, all different from your way, so here they are:
DISCLAIMER I use Reflux library and not the Facebook's one.
Actions and Stores as elements
My first attempt was to make Flux pattern into elements so that any view, which need access to a store and invokes actions simply imports them.
<dom-module id="a-view">
<template>
<my-actions id="actions"></my-actions>
<my-store model="{{model}}"></my-store>
<span>{{model.property}}</span>
<button on-click="executeAction"></button>
</template>
</dom-module>
<script>
Polymer({
is: 'a-view',
executeAction: function() {
this.$.actions.doSomething({});
}
});
</script>
<my-actions> and <my-store> simply encapsulate actions and stores. There are some downsides to this method. First, potentially numerous non-visual elements are created, which can have detrimental effect on performance. Also creating those elements can be tricky if they should be Polymer elements, because they need static state. For a complete example see this repo
Flux without Flux
Recently I realized, again, what Web Components really are. With WC, your main API is the browser, namely elements, attributes and events. And Flux essentially is an event-driven data flow. So why not use Custom Events to communicate between custom elements? Here's an excerpt from my yesterday's plunk
<template is="dom-bind">
<a-view clicks="[[clicks]]" id="one"></a-view>
<a-view clicks="[[clicks]]" id="two"></a-view>
<a-view clicks="[[clicks]]" id="three"></a-view>
<a-store click-history="{{clicks}}"></a-store>
</template>
<script>
Polymer({
is: 'a-view',
properties: { clicks: Object },
fireClick: function() {
// invoking action is simply firing an event
this.fire('a-view-click', {});
}
});
Polymer({
is: 'a-store',
attached: function(){
document.addEventListener('a-view-click', function(ev) {
// do work and update store here
}.bind(this));
}
});
</script>
This is nice, because is not limited in any way to Polymer. Custom elements can be created with native API or other library and simply communicate with browser acting as your dispatcher. Of course this doesn't give you ways of synchronization out of the box, but is a simple and clean way without any clutter.
As you will see on Plunker, store updates by data-bindings. Another possibility is to fire off another event, though I'm not sure which would be better or when
Use Polymer's behaviors
Finally I've just had an idea, which improves upon the first, by replacing action/store custom elements by behaviors. There's no code yet, but here's a sketch:
var MyActionsBehaviour = PolymerFlux.createActions({ /*...*/ });
var MyStore = PolymerFlux.createStore({ /*...*/ });
Polymer({
is: 'a-view',
behaviours: [ MyActionsBehaviour, MyStore ],
onClick: function() {
this.behaviourAction.invoke({});
}
}});
Polymer({
is: 'a-store',
behaviours: [ MyActionsBehaviour, MyStore ],
attached: function() {
this.behaviourAction.listen(function() {
// 1. do work
// 2. update views
});
}
}});
I left the view updating part blank. It would likely take place by signalling an event but another possibility would be firing another action (Reflux has a nice concept of nested actions). Also I'm currently leaving the PolymerFlux.createActions and PolymerFlux.createStore for your imagination ;). The exact internals would ofc depend on the Flux implementation you choose.
I have made an attempt to use flux-type architecture in a polymer application.
Here is the main-app.html:
<link rel="import" href="./bower_components/polymer/polymer.html">
<link rel="import" href="store-cart.html">
<link rel="import" href="store-cart2.html">
<link rel="import" href="view-cart.html">
<link rel="import" href="view-additems.html">
<dom-module id="main-app">
<style>
</style>
<template>
<!-- Stores-->
<store-cart id="cart1" action=[[action]]></store-cart>
<store-cart2 id="cart2" action=[[action]]></store-cart2>
<!--Views and other stuff-->
<view-additems cart="cart1"></view-additems>
<view-additems cart="cart2" add="3"></view-additems>
<view-cart update="[[updateView]]"></view-cart>
</template>
</dom-module>
<script>
Polymer({
is: 'main-app',
properties: {
action: {
type: Object,
value: {}
},
updateView: {
value: ""
}
},
listeners: { //dispatcher event -> action
'viewAction': 'viewAction', // Action from view to be dispatched to the store/stores
'storeUpdated': 'storeUpdated' // storeUpdated-event from store to views
},
viewAction: function(e) {
action = e.detail;
switch (action.type) {
// "CombineCarts" is needed because both of the stores needs to be updated in order
case 'combineCarts':
this.$.cart1.addItems(this.$.cart2.nbItems);
this.$.cart1.updateViews();
this.$.cart2.emptyCart();
this.$.cart2.updateViews();
break;
// default action when store/stores can be updated independently
default:
this.action = action;
}
},
storeUpdated: function(e) {
this.updateView = e.detail;
}
});
</script>
The whole example: https://github.com/grohjy/polymer_flux_example
The main idea is that a "dispatcher" is located at the top most level of the polymer application and it's role is to redirect messages from stores to views and viceversa. Each store and view defines to which messages they reacts and how. At the dispatcher there is also an example how to update multiple stores in needed order.
The stores and some of the views are also located at the top most level of the application. A view can also have child views. A store shouldn't have any visual dom elements.
Please feel free to comment and share ideas.
I have a little bit of markup that looks like this:
<polymer-element name="blog-post" noscript>
<template>
<mark-down>
<textarea value="{{post}}"></textarea>
</mark-down>
<polymer-localstorage name="my-blog-editor" value="{{post}}">
</polymer-localstorage>
</template>
</polymer-element>
I'd like the mark-down tag to be able to see the value of the textarea but I'm having a hard time knowing when to query for it.
Inside of mark-down my code looks something like this:
attached: function() {
this.textarea = this.$.textareaContent.getDistributedNodes()[0]; // this grabs the textarea element
// create an observer instance
var observer = new MutationObserver(function(mutations) {
mutations.forEach(function(mutation) {
console.log(mutation);
});
});
// pass in the target node, as well as the observer options
observer.observe(this.textarea, { attributes: true });
}
Unfortunately the mutation observer never fires. I've tried checking for the value of textarea directly in attached and domReady but it's always null. The only success I've had is to use a setTimeout to check for the value asynchronously.
textarea is specifically difficult to use in this manner, because you cannot observe it's content changing with MutationObservers, only with events.
Worse still, there is no signal at all for setting textarea.value (which is what your binding will do).
If you want to use textarea like this, suggest you expose a property on the mark-down element for binding a value, and listen to events from the textarea to monitor user edits.
<mark-down value="{{post}}">
<textarea></textarea>
</mark-down>