While migrating to Polymer 1.0 from 0.5 I have come across an interesting thing. Thought it might help others having similar problem.
I have an element where I am using <template is="dom-repeat" items="{{customers}}">...</template>. The problem I am facing is I have to place every single property binding inside a HTML element. The code below what I intended to write:
<template is="dom-repeat" items="{{customers}}">
<div>
{{item.name}}<br />
{{item.addr}}, {{item.addr2}}<br />
{{item.phone}}
</div>
</template>
But it is only displaying the value for {{item.name}}. The reason is other property bindings are not wrapped within separate HTML tags, they are not displaying at all!
I tried the following but didn't work either:
<template is="dom-repeat" items="{{customers}}">
<div>
<p>{{item.name}}</p>
<span>{{item.addr}} {{item.addr2}}</span>
</div>
</template>
Means, I put {{item.name}} inside a <p>...</p> tag and placed {{item.addr}} and {{item.addr2}} inside a single <span>...</span> tag.
Then I went on and put every single property binding wrapped by their own HTML tags like the following:
<template is="dom-repeat" items="{{customers}}">
<div>
<p>{{item.name}}</p>
<span style="display:block">{{item.addr}}, <span>{{item.addr2}}</span></span>
<span style="display:block;">{{item.phone}}</span>
</div>
</template>
and it works!!
I truly have no idea whether it is a bug of 1.0 or there is something I am doing wrong! If anybody knows the answer please help.
Thanks in advance
You're not doing anything wrong. With the introduction of Polymer 0.9 (and later 1.0) data-binding to the content of text nodes only works if you wrap everything into its own element.
See the Polymer documentation:
The binding annotation must currently span the entire content of the tag
So you have to remove all whitespace and other characters for it to work.
Example from the documentation:
<!-- this works -->
<template>
First: <span>{{first}}</span><br>
Last: <span>{{last}}</span>
</template>
<!-- Not currently supported! -->
<div>First: {{first}}</div>
<div>Last: {{last}}</div>
<!-- Not currently supported! -->
<div>
{{title}}
</div>
Edit
As of Polymer 1.2, the issue described in the question is no longer problematic / erroneous. Compound bindings now work, see release notes on the Polymer blog.
Just a heads up, for element attributes though you can use something like a helper function for string concatenation. Here's an example.
<my-foo fullname="{{computeFullName(firstname, lastname)}}">
Hi, my name is <span>{{firstname}}</span>.
</my-foo>
...
computeFullName: function(first, last) {
return first + ' ' + last;
}
And here's the link: https://www.polymer-project.org/1.0/docs/migration.html#data-binding
EDIT:
For node content as well, string concatenation can be done using computed properties (I call them helper functions). Here's an example,
<dom-module id="x-custom">
<template>
My name is <span>{{fullName}}</span>
</template>
</dom-module>
<script>
Polymer({
is: 'x-custom',
properties: {
first: String,
last: String,
fullName: {
type: String,
// when `first` or `last` changes `computeFullName` is called once
// (asynchronously) and the value it returns is stored as `fullName`
computed: 'computeFullName(first, last)'
}
},
computeFullName: function(first, last) {
return first + ' ' + last;
}
...
});
</script>
With Polymer 1.2 you example code will actually work. Binding annotations no longer need to span the entire tag.
Example:
<div>first name: [[name.first]] last name: [[name.last]]</div>
https://blog.polymer-project.org/releases/2015/11/02/release-1.2.0/
You'll want to use a computed property to combine values. Search for them on this page https://www.polymer-project.org/1.0/docs/devguide/properties.html
Related
I'm trying to use VueJs conditional rendering using handlebars in vueJs 2.0 as per their documentation but eslint is coming back with and error:
- avoid using JavaScript keyword as property name: "if" in expression {{#if ok}}
- avoid using JavaScript keyword as property name: "if" in expression {{/if}}
VueJs does not seem to be rendering it.
<!-- Handlebars template -->
{{#if ok}}
<h1>Yes</h1>
{{/if}}
If you are trying to use Vue.js syntax, the documentation outlines just a few lines down what's done for Vue.js. You would use the v-if directive.
<h1 v-if="ok">Yes</h1>
If like you mentioned, you're wanting to use Handlebars alongside Vue.js, note that both of them use the same {{ curly braces in templates. You may need to change Vue's use of the curly braces like so...
Vue.config.delimiters = ['<%', '%>'];
Either:
Using v-if to conditionally render
<h1 v-if="isVisible"> Yes </h1>
or using v-show to add a hidden attribute to that element style
<h1 v-show="isVisible"> Yes </h1>
either can be used but be careful with v-if since the element won't be in the DOM if the condition is not met.
I believe that is simply to document that the conditional does not go on a parent tag, but rather it is placed directly on the node that you want to conditionally display.
In other words its simply a comparison not part of Vue.js markup, but rather part of Handlebars.
Vue conditional rendering syntax
<h1 v-if="ok">Yes</h1>
<h1 v-show="ok">Yes</h1>
Details in original docs.
https://v2.vuejs.org/v2/guide/conditional.html#v-if-vs-v-show
Firstly, You should look at the vue documentation .https://v2.vuejs.org/v2/guide/conditional.html#v-if-vs-v-showjs and by the way, you can use "v-if" and "v-show"attributes, in flowing related to
examples.
<h1 v-if='isShow'>Test</h1>
<h1 v-show='isShow'>Test</h1>
For anyone coming here from a search trying to conditionally render inside {{ }} braces, you could always use a computed property:
import { computed } from 'vue';
<script setup>
const submitButtonText = computed(() => {
return props.formObject ? 'Save' : 'Create';
});
</script>
<template>
<form>
<button type="submit">
{{ submitButtonText }}
</button>
</form>
</template>
v-if and v-if-else work perfect for large elements, but this is great for simple one-line conditional text.
I'm not very new to Vue.js which is probably why I feel like I've been running mad all morning :). While creating a component, which I usually do, quite frequently, in this case, I had to initialize Google Maps within the mounted function, which seems like the right place to do that. In the mounted function, I would access the id property of a nested input field and attach an event listener to it. Pretty simple right?
Well, I figured that when I try to use the component multiple times on my page, I'm somehow accessing the same (seemingly shared) this variable within the mounted function.
Not sure why exactly this happens and/or if it's a feature but to make it even weirder, the props yield correct values within the template. (and within the methods as well)
Component Definition
<template>
<div class="LocationInput">
<input
type="text"
:id="id"
/>
</div>
</template>
<script>
export default {
name: 'LocationInput',
props: ['id'],
mounted() {
console.log('Component object representation ==> ', this)
console.log('ID ==> ', this.id)
}
}
</script>
Using my component...
<template>
<div class="MyTravelApp">
<LocationInput id="id1"/>
<LocationInput id="id2"/>
</div>
</template>
<script>
import LocationInput from './components/LocationInput';
export default {
components: { LocationInput }
}
</script>
What I get at the end of the day is the correct id values in the template but in my console, the exact same object and id are logged as you can see below. Notice how the _uid property is the same thing for both.
To make matters even worse, after modifying the this variable in the mounted function, while inspecting, I observed that the second component has that property modified as well. So they are essentially sharing the same object, which is extremely weird.
I would like to know if anyone has had similar issues and how to deal with it.
No self-closing tags for components.
Vue templates need to be valid HTML. There are no "self closing tags"
in HTML5, it's an XHTML syntax which is now outdated and you should
never use it.
(Later note:)
FYI self-closing tags works in 2.0 as long as you don't use in-dom
templates.
You may also be having an issue with camelCase vs. kebab-case. The snippet below behaves as expected.
Vue.component('locationInput', {
template: '#location-input-template',
props: ['id'],
mounted() {
console.log('Component object representation ==> ', this._uid)
console.log('ID ==> ', this.id)
}
});
new Vue({
el: '#my-travel-app'
});
<script src="//cdnjs.cloudflare.com/ajax/libs/vue/2.2.6/vue.min.js"></script>
<template id="location-input-template">
<div class="LocationInput">
<input type="text" :id="id">
</div>
</template>
<div id="my-travel-app">
<location-input id="id1"></location-input>
<location-input id="id2"></location-input>
</div>
Update
Apparently when using <template> the reading of innerHTML will return all attributes in lower case. Angular2 will not understand ngfor or ngif as of this beta 9 version and throws error. <script> is treated as a text fragment rather than DOM, which means attributes stay as they are.
Here:
https://groups.google.com/forum/#!topic/angular/yz-XdYV2vYw
Originial
Taking the following html and angular2 beta 9 component:
HTML CODE
<my-page>Loading...</my-page>
<script type="text/html" id="my-component-template1">
<select [(ngModel)]="SelectedType">
<option *ngFor="#someType of MyTypes" [selected]="SelectedType == someType" [value]="someType">{{someType}}</option>
</select>
</script>
<template id="my-component-template2">
<select [(ngModel)]="SelectedType">
<option *ngFor="#someType of MyTypes" [selected]="SelectedType == someType" [value]="someType">{{someType}}</option>
</select>
</template>
JS CODE
var myComponent =
ng.core.Component({
selector: 'my-page',
//complains if i use #my-component-template2
template: document.querySelector('#my-component-template1').innerHTML
})
.Class({
constructor: function () {
var self = this;
self.MyTypes = ['first', 'second'];
self.SelectedType = self.MyTypes[0];
}
});
document.addEventListener('DOMContentLoaded', function () {
ng.platform.browser.bootstrap(myComponent);
});
If i use my-component-template1 it works fine, but if i choose my-component-template2 it complains that ngModel and ngForOf are not a known native properties.
I tested a div as a template and apparently that won't work either with the same errors. So question is, why is it breaking if the template is part of the DOM? Furthermore, I really don't want to use the script text/html hack. Assuming this is why <template> was added in html5 specification. Why is this happening and how can i fix it?
The <template> tag is only used by Angular 2 structural directives (like the built-in ngIf, ngFor, ngSwitch, etc) - its use is somehow similar with the html5 specification since it defines content which is stored for subsequent use.
The * in front of a structural directive is just syntactic sugar which allows us to skip the <template> tag and focus directly on the HTML element that we are including, excluding, or repeating - you can read more about it here.
An example from Angular 2 docs which showcases this:
<!-- Examples (A) and (B) are the same -->
<!-- (A) *ngIf paragraph -->
<p *ngIf="condition">
Our heroes are true!
</p>
<!-- (B) [ngIf] with template -->
<template [ngIf]="condition">
<p>
Our heroes are true!
</p>
</template>
At the moment, I'm not sure if there's a way of defining inline Angular 2 HTML templates like there's in AngularJS 1. Your hack, as you put it, seems to do its job.
Angular handles <template> tags itself and doesn't simply add them to the DOM. If you inject TemplateRef into the constructor of your component you should get a reference to the template.
class MyComponent {
constructor(private tmplRef:TemplateRef) {
}
}
So I have an iron-list element for a user's data history. The iron-list is not part of a custom element. It is simply on the page. I want to populate once the user has successfully logged in. Perhaps it is just my inexperience with polymer, but there doesn't seem to be a straightforward way to do this. First attempt (simplified for reading, e.g. I don't actually use jquery, there's lots of error-handling code I'm omitting, etc):
<iron-list as="item" style='height: 100%;' id='history-list'>
<template>
<div style='min-height: 140px;'>
<ul>
<!-- various fields for each record as list items -->
</ul>
</div>
</template>
</iron-list>
<script>
//once user is logged in
var items = $.getJSON('userhistoryscript');
//setAttribute doesn't work either
document.getElementById('history-list').items = items;
</script>
I would swear this worked in an earlier version of Polymer. But it doesn't seem to work now, which is fine, but I need an alternative.
Some alternatives I've considered:
Have iron-ajax element in same DOM scope and set '
the URL once the user is logged in to trigger the
xhr request. I'm not sure whether or not that'd work.
Wrap the list in a custom element and use an
iron-meta-query per chrisW's answer.
Those options are terrible. I cannot believe there is no simpler way to accomplish this feat. How do I conditionally fetch data based on user input and dynamically add an iron-list to the page (or update one that's already there)? Is there really no API for this use case?
UPDATE
Thank you for your answers. Turns out that my original code actually works fine: it was actually a build process issue. For some reason iron-list did not get installed when I installed the project dependencies through bower. I took out the vulcanized import (which must not have contained a ref to iron-list either) and imported all the elements directly, then I got the 404 and figured out what had happened.
I think that for best practices, you should use this.$.historyList to refeer id on this element. Anyway, when you get data to populate iron-listyou should use this.set('items', data); An example using your element looks like:
<iron-list>
<template is="dom-repeat" items="{{data}}" as="history">
<!--history.property-->
</template>
</iron-list>
<script>
Polymer({
properties:{
data:{type:Array, value:[],}
},
_functionToSetDataWhenUserIsLoggedIn: function(data){
this.set('data',data);
}
});
</script>
Edit
An example of iron-list
<template is="dom-bind">
<iron-ajax url="data.json" last-response="{{data}}" auto></iron-ajax>
<iron-list items="[[data]]" as="item">
<template>
<div>
Name: <span>[[item.name]]</span>
</div>
</template>
</iron-list>
</template>
This example is using an ajax call that executes automatically and populates the iron-listwithout the need to create a customized element.
More about iron-list on:
https://elements.polymer-project.org/elements/iron-list
I didn't entirely understand your question. Hope this helps.
<iron-list items="[[data]]" as="item">
<template>
<div>
Name: <span>[[item.name]]</span>
</div>
</template>
</iron-list>
properties:{
data:{type:Array, value:[],}
},
// the attached function is automatically called
attached: function() {
// Use an iron meta in the element that you keep track in of login information
// or create an onLogin listener
var isLoggedIn = new Polymer.IronMetaQuery({key: 'isLoggedIn'}).value,
if (isLoggedIn) {
var jsonData = $.getJSON('userhistoryscript');
this.set('data',jsonData);
}
}
Side note, when access elements by ids in Polymer elements, make sure you do it this way:
this.$.elementId
or
Polymer.dom('#elementId')
Edit since you don't want to create a custom polymer element
Source Code
<template is="dom-bind">
<iron-list id="list">
</iron-list>
</template>
<script>
document.addEventListener('onLogin', function(event) {
var list = document.getElementById('#list');
var jsonDataObjects = $.getJSON('userhistoryscript');
for (var i = 0; i < jsonDataObjects.length; i++) {
var div = document.createElement('div');
div.textContent = jsonDataObjects[i].info; // change this line
list.appendChild(div);
}
});
</script>
is it somehow possible to render the template in a polymer element dynamically at runtime or when some light-dom elements are available?
I have the following situation:
index.html
<mega-menu>
<span class="menuTriggerText">Open Menu</span>
<ul class="test">
<li>TEST1</li>
<li>TEST2</li>
</ul>
<ul class="test">
<li>TEST1</li>
<li>TEST2</li>
</ul>
</mega-menu>
in my polymer-element.html i want to do something as follows:
<template>
<template repeat="{{temp}}"><p>I want to try this</template>
</template>
Polymer('mega-menu, {
created:function(){},
ready: function(){
//getting markup from light-dom
this.temp = document.getElementsByClassName('test');
},
attached:function(){},
detached: function(){},
attributeChanged: function(attrName, oldVal, newVal){}
});
Now, my question is - how do i get this to work? do i need to bind something on my template? or do i need some kind of event-listener or observer on something?
Thanks, Gbeschbacher
This is precisely what content insertion points are for. You can select top-level light DOM markup to render at specific locations in the Shadow DOM. <content select=""></content> takes a CSS selector and grabs nodes from the light DOM.
Your example would be:
<polymer-element name="mega-menu" noscript>
<template>
<content select=".test"></content>
</template>
</polymer-element>
You should not need to pry into the light DOM like this for such a simple case, but for the sake of completeness, we can get your example working with a few important tweaks:
document.getElementsByClassName('test') looks for nodes in the entire document. This is not what you want. You only want children of <mega-menu>. Instead of document use this (e.g. this.querySelectorAll('.test')).
You're giving <template repeat="{{temp}}"> a NodeList. It won't be able to stamp that out. It expects an Array. Something like this.temp = [].slice.call(this.querySelectorAll('.test')); would work.
http://jsbin.com/balodowi/2/edit