I've encountered a problem with rendering some elements in React.
(I use ImmutableJS)
renderComponents: function(components) {
if(components.isEmpty()) return [];
var table = [];
components.map(function(component) {
table.push(<ComponentTableElement key={ component.get('id') } data={ component } />);
if(component.has('children')) {
var children = component.get('children');
table.concat(this.renderComponents(children));
}
});
return table;
},
As I looked for error, I found that this.renderComponents(children) doesn't return anything at all and the code somehow stops.
I mean before that line everything works ok, but then after this line, when i try to console.log something, it doesn't show up. And it doesn't even reach return table.
So what is wrong with that code?
In the context of the function you pass to map, this refers to the window object, not to the current component instance, so this.renderComponents is undefined when you try to call it.
components.map(function(component) {
this === window;
});
You can pass a value to use as this in the body of your function as the second parameter of Array::map.
components.map(function(component) {
table.push(<ComponentTableElement key={ component.get('id') } data={ component } />);
if(component.has('children')) {
var children = component.get('children');
// here, `this` refers to the component instance
table.concat(this.renderComponents(children));
}
}, this);
If you're using ES6, you can also use fat-arrow functions, which are automatically bound to this.
components.map((component) => {
table.push(<ComponentTableElement key={ component.get('id') } data={ component } />);
if(component.has('children')) {
var children = component.get('children');
// here, `this` refers to the component instance
table.concat(this.renderComponents(children));
}
});
Related
So I'm using a data table which has an active element. When that active elment changes I store the name of the active element in a property of my polymer element. Then I display this String property in a div.
Now I know for certain that the property change works, because I console.log it after a change, the div displaying the property doesn't update and continually displays the default value I have set.
export class ProjectsOverview extends PolymerElement {
static get template() {
return html`
...
<div>{{currentProject}}</div>
...
`
}
static get properties() {
return {
currentProject: {
type: String,
value: "placeholder",
notify: true,
reflectToAttribute: true
}
};
}
connectedCallback() {
super.connectedCallback();
const grid = this.shadowRoot.querySelector('vaadin-grid');
grid.addEventListener('active-item-changed', function(event) {
const item = event.detail.value;
grid.selectedItems = [item];
if (item) {
this.set('currentProject', item.name);
} else {
this.set('currentProject', '');
}
console.log(this.currentProject);
});
}
}
My expected result would be that every time the currentProject property is updated, the div displaying the property updates as well.
The active-item-changed callback does not have its context bound to the Polymer instance (i.e., this is the grid and not the Polymer component). Instead of the function expression, use an arrow function to automatically bind this to the correct context.
// grid.addEventListener('active-item-changed', function(event) { // DON'T DO THIS
grid.addEventListener('active-item-changed', (event) => {
/* this is the Polymer instance here */
this.set('currentProject', ...);
})
Your scope is wrong. You're using an anonymous function so when you try to set currentProject, you do that when your this is your anonymous function. Use .bind(this) to fix your problem.
grid.addEventListener('active-item-changed', function(event) {
const item = event.detail.value;
grid.selectedItems = [item];
if (item) {
this.set('currentProject', item.name);
} else {
this.set('currentProject', '');
}
console.log(this.currentProject);
}.bind(this));
I'm doing a very simple react+redux application where I've a reducer called goals and a container called GoalsContainer.
From App Container I call the action goal for load the initial goals from a local db(indexedDB)
dispatch(loadGoals(currentDate));
This call the loadGoals from the goals actions:
export function loadGoals(currentDate = new Date()){
return dispatch => {
var goals = getGoalsFromDB(normalizeDate(currentDate)); // with this I get an array from the db
dispatch(setLoadGoals(goals));
}
}
function setLoadGoals(goals) {
return {
type: types.LOAD_GOALS,
goals
};
}
And then in my reducer I've this:
export default function goals(state = [], action) {
switch(action.type) {
case types.LOAD_GOALS:
return action.goals; // here I set the state of the goal reducer with the array passed via action
default:
console.log('Im here');
return state;
}
}
and this is my GoalsContainer(read the comments in code):
class GoalsContainer extends React.Component {
render() {
if (this.props.goals != undefined) {
console.log('ok called the render'); // in chrome console shows it
console.log(this.props.goals); // in chrome console shows correctly the goals loaded
console.log(this.props.goals.length); // it say 2
if (this.props.goals.length > 0) { // here fails...
console.log('good');
console.log(this.props.goals);
var goalsView = <div>There are goals</div>
}
else {
console.log('why go here?'); // go here
console.log(this.props.goals);
var goalsView = <div>No goals</div>
}
} else {
var goalsView = <div>Undefined</div>
}
return (
<div id="goals-main">
{goalsView}
</div>
);
}
}
GoalsContainer.propTypes = propTypes;
function mapStateToProps(state) {
const { goals, environment } = state;
const { currentDate } = environment;
return {
goals,
currentDate
}
}
export default connect(mapStateToProps)(GoalsContainer);
The problem is that when it does the if check, it fails(like if there are 0 goals), but in chrome console show correctly the goals array...
Then if I force with some workaround the render(), all works correctly.
What I've done wrong ?
You didn't mention if you use https://github.com/gaearon/redux-thunk or not. To use reducer returning function you should definitely install it.
It's hard to follow all of the parts of your code from random gists. What happens if you change your GoalsContainer to be;
class GoalsContainer extends React.Component {
render() {
console.log(this.props.goals);
return (
<div id="goals-main">
{(this.props.goals.length >= 1)?<div>There are goals</div>:<div>Nope!</div>}
</div>
);
}
}
What gets logged to the console?
Router.route('/courses/:_catalog', function () {
var courseCatalog = this.params._catalog.toUpperCase();
Meteor.subscribe("courseCatalog", courseCatalog);
this.render('CourseDetail', {
to: 'content',
data: function () {
return Courses.findOne({catalog: courseCatalog});
}
});
}, {
onAfterAction: function() {
if (!Meteor.isClient) {
return;
}
debugger
var course = this.data(); <======
SEO.set({
title: "course.catalog"
});
}
});
In the above code, please look at the debugger statement. I want to access the data but it seems I am doing something wrong because this.data doesn't exist. I also tried Courses.find().fetch() but I only get an empty array inside onAfterAction. What's the right syntax and what am I missing?
It needs to be inside a this.ready() block:
onAfterAction: function() {
if (this.ready()) {
var course = this.data();
...
}
}
You need to subscribe to data first. Have a look at the waitOn function to do this. The server only sends the documents you subscribed to, and since you didn't subscribe, Courses.find().fetch() returns an empty array.
Also, don't put SEO stuff in onAfterAction. Put it in onRun which is guaranteed to only run once.
I'm new to Meteor and I want to create a slideshow with items from a collection, in this case simple words. The slideshow should be controlled by back and forward buttons and replace the current word.
In JavaScript/jQuery I would create an array of objects and a control index, with limits via if-statements, so the index never can drop below zero or overflow the length of the array.
See fiddle for working example:
http://jsfiddle.net/j0pqd26w/8/
$(document).ready(function() {
var wordArray = ["hello", "yes", "no", "maybe"];
var arrayIndex = 0;
$('#word').html(wordArray[arrayIndex]);
$("#previous").click(function(){
if (arrayIndex > 0) {
arrayIndex -= 1;
}
$('#word').html(wordArray[arrayIndex]);
});
$("#next").click(function(){
if (arrayIndex < wordArray.length) {
arrayIndex += 1;
}
$('#word').html(wordArray[arrayIndex]);
});
});
Meteor
I'm curious how to implement this in regards to best practice in meteor and abide to the reactive pattern as I'm still trying to wrap my head around this interesting framework. My first hurdle is to translate the
if (arrayIndex < wordArray.length)
// to
if (Session.get("wordIndex") < ( (((length of collection))) )
According to the docs I should do a find on the collection, but I have only manage to return an empty array later with fetch. Sorry if this got long, but any input would be appreciated to help me figure this out.
collection.find([selector], [options])
cursor.fetch()
This is the code I have so far:
Words = new Mongo.Collection("words");
if (Meteor.isClient) {
// word index starts at 0
Session.setDefault("wordIndex", 0);
Template.body.helpers({
words: function () {
return Words.find({});
},
wordIndex: function () {
return Session.get("wordIndex");
}
});
Template.body.events({
"submit .new-word": function (event) {
// This function is called when the word form is submitted
var text = event.target.text.value;
Words.insert({
text: text,
createdAt: new Date() //current time
});
// Clear form
event.target.text.value = "";
// Prevent default form submit
return false;
},
'click #previous': function () {
// decrement the word index when button is clicked
if (Session.get("wordIndex") > 0) {
Session.set("wordIndex", Session.get("wordIndex") - 1);
}
},
'click #next': function () {
// increment the word index when button is clicked
if (Session.get("wordIndex") < 10 ) {
Session.set("wordIndex", Session.get("wordIndex") + 1);
}
}
});
}
if (Meteor.isServer) {
Meteor.startup(function () {
});
}
.count() will return the number of documents in a collection.
`db.collection.count()`
There is something called Collection helpers, which works similar to other helpers (eg., template, etc.,). More elaborate explanation is covered here: https://medium.com/space-camp/meteor-doesnt-need-an-orm-2ed0edc51bc5
I would like to display a pulse transition when my collection change.
In my html file, I have that:
<template name="menuItemTag">
<div class="app-menu-item-tag ui label">{{ count }}</div>
</template>
In my js file, I expose the count variable for my template like that:
Template.menuItemTag.count = function() {
return MyCollection.find().count();
};
With that the count change in the ui when the collection is updated.
Now, I would like to display a pulse transition on my div label each time the count value change.
I tried to use the cursor.observe
Template.menuItemTag.rendered = function() {
MyCollection.find().observe({
added: function (id, user) {
$('.app-menu-item-tag:nth(0)').transition('pulse');
},
removed: function () {
$('.app-menu-item-tag:nth(0)').transition('pulse');
}
});
};
Unfortunately, it is call too many times when the template is rendered the first time.
If initialy I have 40 items in my collection, the transition is played 40 times...
Is there a clean way for playing a ui transition on changes and avoid the collection initialisation?
Try this:
Template.menuItemTag.count = function() {
return Session.get('count');
};
Template.menuItemTag.rendered = function() {
this.countComputation = Deps.autorun(function() {
Session.set('count', MyCollection.find().count());
$('.app-menu-item-tag:nth(0)').transition('pulse');
});
};
Template.menuItemTag.destroyed = function() {
this.countComputation.stop();
};
Thanks sbking for your answer, I still have a problem on initialization of the collection.
I propose below to defer the first animation util the collection will be completely filled:
Template.menuItemTag.count = function() {
return Session.get('count');
};
Template.menuItemTag.rendered = function() {
var that = this;
this.countComputation = Deps.autorun(function() {
Session.set('count', MyCollection.find().count());
// Cancel playing UI transition. The collection is not completely initialized
if (that.handleTimeout) {
Meteor.clearTimeout(that.handleTimeout);
}
// Play the UI transition without the timeout if the collection is initialized
if (that.noNeedTimeoutAnymore) {
$('.app-menu-item-tag:nth(0)').transition('pulse');
}
// Tentative to play the UI transition during the collection feeding
else {
that.handleTimeout = Meteor.setTimeout(function() {
$('.app-menu-item-tag:nth(0)').transition('pulse');
// At this point we know that the collection is totaly initialized
// then we can remove the timeout on animation for the future update
that.noNeedTimeoutAnymore = true;
}, 1500); // You can adjust the delay if needed
}
});
};
Template.menuItemTag.destroyed = function() {
this.countComputation.stop();
};