When a meteor app is deployed on server, it takes a considerable amount of time (3-4 seconds) for the data to be fetched from mongodb. In my app, I have a template that is bound to data through an #each block helper.
{{#each items}}
{{> item_info}}
{{else}}
No items yet.
{{/each}}
So when the app loads in a new browser session, users see the message No items yet till the time data has finished loading. When data becomes available, that message gets replaced with the actual data. But this results in a bad user experience because some users actually think, for those 3-4 seconds, that they have lost their data.
My question is -- is it possible to change that "else" message to something like "Loading..." while data is being fetched? Or is there a more elegant solution to this problem?
Thanks.
I think you should use Session with onComplete() function inside the Meteor.subscribe()
This will executed automatically when the subscription is completed, i.e ur collections are completed loading on client.
For Eg.
Meteor.subscribe('yourCollection', function onComplete(){
// set a session to true indicating your collection is loaded.
Session.set('itemsLoaded', true);
});
Then call your template helper based on the session value as:
Template.yourTemplate.isLoaded = function(){
return Session.get('itemsLoaded');
}
And your html will look like:
<template name="yourTemplate">
{{#if isLoaded}}
{{#each items}}
{{> item_info}}
{{/each}}
{{/if}}
{{#unless items}}
<img src="images/loader.gif">
{{/unless}}
</template>
Related
This code is from the Meteor first app tutorial, and I am a bit confused about the role of the words "task(s)".
In the html file it is the name of a template, which is called by {{> task}}
in <body>
In the js file, it is used to declare a collection:
Tasks = new Mongo.Collection("tasks");
By which is meant "Tasks" is a collection of "tasks"
tasks is also the name of a function in the js file -> tasks: function ()
which returns a list of "tasks" to the html file, where it is called in this way:
{{#each tasks}}
{{> task}}
{{/each}}
It seems the meaning of "tasks" is both the name of a function, and the data tuples it returns. Is that normal? Is this statement in <body> the template "task" is called to format data returned by a function "tasks" that returns a list of "tasks". Is that normal?
html file:
<body>
<div class="container">
<header>
<h1>Todo List</h1>
</header>
<ul>
{{#each tasks}}
{{> task}}
{{/each}}
</ul>
</div>
</body>
<template name="task">
<li>{{text}}</li>
</template>
js file
Tasks = new Mongo.Collection("tasks");
if (Meteor.isClient) {
// This code only runs on the client
Template.body.helpers({
tasks: function () {
return Tasks.find({});
}
});
Agree that the example reuses names, this is quite a common pattern. Perhaps an explanation of each name might help:
Tasks = new Mongo.Collection("tasks");
tasks on the right-hand-side is the name of the mongodb collection. If you go into the mongo shell for example you will see documents in the db.tasks collection
Tasks on the left-hand-side is the name of the collection to be used in javascript in your Meteor app, both on the client and server. A typical use of Tasks will be javascript code such as Tasks.find({})
The tasks which appears in the spacebars template code in your HTML file is quite different.
{{#each tasks}}
{{> task}}
{{/each}}
tasks refers to a template helper function that returns a cursor or array
task refers to an individual Template that you've created in HTML. You can tell it's a template because of the template reference >
You could replace tasks and task in your template with taskList and oneTask and that would be just fine. But you couldn't just start using MyTasks.find() in javascript without renaming your Tasks collection on the left side of the collection assignment.
There's an unofficial convention that mongo collection names are lower case whereas Meteor collection names (in js) are Proper case. Collection names are global variables in js so the Proper case helps distinguish them anyway.
I can see how that is confusing at first and one may prefer a different naming of variables, functions, helpers and collections to avoid confusion. But yeah, the > tasks refers to the template (to be embedded). In the body you need to use #each tasks to refer to the helper function (tasks). So really there are only three items here:
Tasks, the collection holding the data,
tasks, the helper function that makes data from the Tasks collection available to the template engine (referred to in the body using #each tasks),
and task the template that renders a given task.
I have a simple template which has a search box in it:
<template name="search">
<input type="text" name="search" id="search" />
{{> search_results}}
</template>
and obviously, the search results template:
<template name="search_results">
<ul>
{{#each results}}
<li>{{this.resultValue}}</li>
{{/each}}
</ul>
</template>
There is an event for keyp on the search input:
Template.search.events({
'keyup input#search': function (e) {
// fetch result from db
}
});
My problem is, where i have the comment: fetch result from db how do i get the search results template to auto update with the results from the db query?
To be clear: i can get the results fine, just cant see how to get the results template to update.
Essentially, something in the template you want to rerender (search_results) has to be reactive and register a changed event. Out of the box, that means it could be any of the data sources listed here. Since this isn't happening for you, I assume that when you "fetch results from db" you're not actually returning the result of a minimongo query, as this would be reactive by default.
If so, this kind of problem is often most easily solved by rolling your own reactivity using the Deps.Dependency prototype, which (as I understand it) underpins all the other reactive data sources other than the minimongo itself.
If you set var resultsChanged = new Deps.Dependency(), you get an object with two methods: depends and changed. Invoke the former in any computation you want to rerun when it changes and the latter to register a change. Session variables are basically just key/value stores with these Deps.Dependency methods attached to their get and set methods respectively.
So if you have resultsChanged initialised, you just need to make sure your search_results template depends on it, either by adding a new helper function (if results is in the data context as opposed to being a call to a helper), or amending the results helper itself. I'll assume the latter, but adding a new helper instead would be equally trivial.
Template.search_results.helpers({
results: function() {
resultsChanged.depend();
// get your results from wherever
return results;
}
});
That will rerun every time resultsChanged changes, so you just have to add the appropriate code in your callback when you fetch the results:
'keyup input#search': function (e) {
// fetch result from db, passing "resultsChanged.changed()" in a callback
}
Obviously, if the result fetching is synchronous, you don't even need to pass a callback, you can just do it on the next line.
I hope that is vaguely helpful - please let me know if it's not. If my assumption that you're not just pulling something out of the database is wrong, then this is probably on totally the wrong track, so I would recommend posting your actual "fetch result from db" code in your question.
I've got a Newsfeed idea that I wanted to build with Meteor, but I'm having a bit of a struggle figuring out how to make the news feed itself constant, that is not reactive, but update the sub-items (comments, likes, etc) as soon as they're updated.
I've got everything stored in a single collection, and I'd like to keep it that way if possible. So the collection is setup like this:
[
{
title: 'A random title',
date_created: '01/01/2001',
comments:
[
{'message': 'Lorem ipsum', date_created: '01/01/2001'},
[...]
]
},
[...]
]
So what I'd like to do is have the newsfeed non-reactive, so that when a new news item is inserted or updated, the template holding the list of news won't get re-rendered. But if a comment is added, deleted, or someone likes the news feed, I'd want that to get updated right away in the template.
I've been trying to figure out how to use {{#isolate}} and {{#constant}} but to no prevail.
Here's my client side JS:
Template.group_feed.feed_data = function() {
var feed = Newsfeed.find({}, {
sort: {updated_time: -1},
limit: 10,
reactive: false
}).fetch();
return feed;
};
I set reactive: false so that it doesn't update the template, but that makes it static also when comments or likes are updated. So I'm guessing there's a better way to do this then to make the whole collection non-reactive.
Here's my template code:
<template name="group_feed">
<div id="feed-wrapper">
<ul>
{{#each feed_data}}
{{> group_feed_item}}
{{/each}}
</ul>
</div>
</template>
<template name="group_feed_item">
<li>
<h1>{{title}}</h1>
<div class="comments">
{{#each comments}}
<p>{{message}}</p>
{{/each}}
</div>
</li>
</template>
Anyone got a nice way of achieving this?
You have two options here. (I'll use coffeescript for my pseudocode)
use observeChanges:
NewsCursor = NewsItems.find()
NewsCursor.observeChanges
changed: (id, fields) ->
if fields.comments
Session.set ("commentsForId"+id), fields.comments
Split your data into two collections: one for the posts and one for the comments.
If you don't do one of those, {{isolate}} isn't going to help you. With your current data setup, Meteor just sees whether the post changed or not, and updates any templates when it does; it doesn't keep track of which part changed.
I did not test it, but I guess it would be most straightforward to limit the subscription of the client, thus reducing data transfer an eliminataing the need for the preserve:
it would be something like:
on server:
Meteor.publish('tenItemsBefore',function (time) {
Newsfeed.find({updated_time: {$lt time}}, {
sort: {updated_time: -1},
limit: 10
})}
on client, in reactive context eg. in Meteor.autorun():
Newsfeed.subscribe('tenItemsBefore',Session.get('lastUpdate'));
on client, triggered by an event eg. refresh using router package:
Session.set('lastUpdate', (new Date()).getTime());
hope that helps,
best, Jan
I'm pretty sure the problem is that you are returning an array rather than a cursor.
It seems that Spark behaves differently with the two.
Remove the .fetch() from the end of the feed query.
For more information about how this stuff works, I would strongly suggest looking at Chris Mather's great presentations at http://www.eventedmind.com/
Specifically, the one on reactivity in slow motion illustrates the difference between an array and a cursor:
http://www.eventedmind.com/posts/meteor-ui-reactivity-in-slow-motion
UPDATE: In my original answer I didn't fully understand problem - my apologies, so the bit about removing the fetch() will not help you. Here are a couple of options you might want to explore:
Using the Meteor.observe or Meteor.observeChanges to watch for changes to the comments field and updated the DOM with code ('by hand').
Create a custom collection on the server side that publishes just the comments from your original collection. So I'm not suggesting you change the data model as stored in mongo, just publish a different view of it. With this way it might be easier to continue to use templates to update the comments.
After initial loading of the collection, make a note of the viewed item ids, and then subscribe to the collection passing a list of ids to watch (or date range). This would require a new publish function that took a array of ids, and filtered the returned documents. This approach would prevent new documents disturbing what you had on screen, and you would still get comment changes, but you would also get deletions and field changes that affected non-comment fields.
Hopefully one of these approaches may fit the bill for you.
In case for some reason you don't want / cannot restrict the data seen by the client with publish or if new posts with earlier post time could be inserted and destroy the preservation the above solution wont work.
Therefore I suggest a different solution to more directly achieve preservation:
On opening the posts save the _id's of the watched posts in a non reactive way as by:
Session.set('watched',
_.map(
Newsfeed.find({}, {
sort: {updated_time: -1},
limit: 10,
reactive: false //not sure wheather you need both, as #StephenD
}).fetch(), // pointed out sth. fetched is non reactive by default
function (obj) {return obj._id;}
)
);
and:
Template.group_feed.feed_data = function () {
return Session.get('watched');
};
Template.group_feed_item.item = function () {
return Newsfeedd.findOne(this);
};
as well as a small update in the html (where with saves you from definining an extra template):
<template name="group_feed_item">
<li>
{{#with item}}
<h1>{{title}} - {{_id}}</h1>
<div class="comments">
{{#each comments}}
<p>{{message}}</p>
{{/each}}
</div>
{{/with}}
</li>
</template>
best, Jan
From the docs (emphasis mine) - http://docs.meteor.com/#find
Cursors are a reactive data source. On the client, the first time you
retrieve a cursor's documents with fetch, map, or forEach inside a
reactive computation (eg, a template or autorun), Meteor will register
a dependency on the underlying data. Any change to the collection that
changes the documents in a cursor will trigger a recomputation. To
disable this behavior, pass {reactive: false} as an option to find.
Note that when fields are specified, only changes to the included
fields will trigger callbacks in observe, observeChanges and
invalidations in reactive computations using this cursor. Careful use
of fields allows for more fine-grained reactivity for computations
that don't depend on an entire document.
I want to perform a Meteor collection query as soon as possible after page-load. The first thing I tried was something like this:
Games = new Meteor.Collection("games");
if (Meteor.isClient) {
Meteor.startup(function() {
console.log(Games.findOne({}));
});
}
This doesn't work, though (it prints "undefined"). The same query works a few seconds later when invoked from the JavaScript console. I assume there's some kind of lag before the database is ready. So how can I tell when this query will succeed?
Meteor version 0.5.7 (7b1bf062b9) under OSX 10.8 and Chrome 25.
You should first publish the data from the server.
if(Meteor.isServer) {
Meteor.publish('default_db_data', function(){
return Games.find({});
});
}
On the client, perform the collection queries only after the data have been loaded from the server. This can be done by using a reactive session inside the subscribe calls.
if (Meteor.isClient) {
Meteor.startup(function() {
Session.set('data_loaded', false);
});
Meteor.subscribe('default_db_data', function(){
//Set the reactive session as true to indicate that the data have been loaded
Session.set('data_loaded', true);
});
}
Now when you perform collection queries, you can check if the data is loaded or not as:
if(Session.get('data_loaded')){
Games.find({});
}
Note: Remove autopublish package, it publishes all your data by default to the client and is poor practice.
To remove it, execute $ meteor remove autopublish on every project from the root project directory.
Use DDP._allSubscriptionsReady() (Meteor 0.7)
As of Meteor 1.0.4, there is a helper that tells you exactly when a particular subscription is ready: Template.instance().subscriptionsReady().
Since this question is a duplicate, please check my answer in the original question, Displaying loader while meteor collection loads.
You can also do template level subscriptions:
Template.name.onCreated(function(){
var self = this;
this.autorun(function(){
const db = this.subscribe('publicationname', [,args]);
if(db.isReady()){
"You'll know it's ready here" .. do what you need.
}
});
})
This makes it easier to know inside the template too. you can just call
{{#if Template.subscriptionsReady}}
{{else}} Loading Screen may be
{{/if}}
You could check when a result is finally returned if you know that your Games collection is never empty:
Meteor.autorun(function() {
if(Games.findOne() && !Session.get("loaded")) {
Session.set("loaded",true);
//Its ready..
console.log(Games.findOne({}));
}
});
You can also use this in your templates:
Client js:
Template.home.isReady = function() { return Session.get("loaded") };
Html
<template name="home">
{{#if isReady}}
Yay! We're loaded!!
{{else}}
Hold an a second
{{/if}}
</template>
Here is another tidbit of information for those who may be using userid or some part of user info stored in Meteor.users database. When the page first loads the Meteor subscribe, going on in the background, may not be complete itself. Therefor when you try to connect to another database to query for that, it will not pull the information. This is because the Meteor.user() is still null itself;
The reason, like said above, is because the actual Meteor users collection has not gotten through pulling the data.
Simple way to deal with this.
Meteor.status().connected
This will return true or false, to let you know when the Meteor.user collection is ready. Then you can go on about your business.
I hope this helps someone, I was about to pull my hair out trying to figure out how to check the status. That was after figuring out the Meteor user collection itself was not loaded yet.
I'm having a few problems when trying to get data from a Meteor Collection and I need some advice.
The collection has been defined, published, and subscribed successfully. If I send the data to a template, it displays fine:
Template.Lists.Projects = function(){
return Projects.find();
};
But I am trying to use the data before displaying it, and this is where I run into problems. First, I'm getting some inconsistencies between find() and findOne(). find(selector) works fine and returns a cursor, but findOne(selector) returns "undefined." I really am only looking for 1 entry, so find() seems unnecessary.
Returns LocalCollection.Cursor:
var find = Projects.find({_id: "3fd33eed-9735-4376-860e-3be383beae2f"});
console.log(find);
Returns undefined:
var find = Projects.findOne({_id: "3fd33eed-9735-4376-860e-3be383beae2f"});
console.log(find);
My next problem arises when using .fetch() on the LocalCollection.Cursor. It returns an empty array.
var find = Projects.find({_id: "3fd33eed-9735-4376-860e-3be383beae2f"});
var fetch = find.fetch();
console.log(fetch);
all this returns is the following line:
[ ]
When I try to specify a specific key from the array I want to display, like:
var find = Projects.find({_id: "3fd33eed-9735-4376-860e-3be383beae2f"});
var fetch = find.fetch();
console.log(fetch.name);
It returns undefined.
I'm still familiarizing myself with Meteor and have never used MongoDB (or minimongo), so I'm probably just making some stupid mistake. If anyone can point it out to me I would be thrilled!
Your results for find() and findOne() are consistent. Basically, Mongo or minimongo is simply not finding a document that matches that _id. FindOne() is precisely like doing a find(selector, options).fetch()[0].
Your Lists.Projects template is likely expecting a collection, array or hash it can iterate over. You cannot return one specific document. If you are using {{#each Projects}} you must provide some way for the template to iterate not just a single value.
I recently had the same problem,
The collection find() returned nothing when used from a query.observe.
The problem was the order of the subscribe of collections.
For example if you have a collection called Lists and one called Projects,
If you're getting the projects by observing a query on lists, and you had :
Meteor.subscribe('Lists');
Meteor.subscribe('Projects');
What happens is the query observe trigger is called, but the Projects are not yet fetched from the server. So Projects.find().fetch().length = 0.
To fix it, simply do
Meteor.subscribe('Projects');
Meteor.subscribe('Lists');
if u've removed autopublish, what if u publish the collection to all user without using a publish name?
Meteor.publish null, ->
Products.find {}
where u subscribe your collection ?
template helper
Handlebars.registerHelp = 'products', (id) ->
Product.find _id: Session.get 'productId'
like if we have price in each product.
the template part looks like...
<template name="products-list">
<div class="products-list">
{{#each products}}
{{> product-item}}
{{/each}}
</div>
</template>
<template name="product-item">
<div class="product-item">
{{price}}
</div>
</template>
the js part, i'll use coffeescript...
Template['product-item'].price = ->
console.log # # # is this as it is product itself, if we have product inserted.
console.log this
return 'the price is: ' + #price
try this way
Meteor.subscribe('testData', function() {
var document = Documents.find();
console.log(document);
});
You are working on the client and you never know when the client got all the data you need. Your functions can be fired when the collections are empty or still not finished synchronized. So you have to make a deferred request to your minimongo (when all data is available local)
And yes you can´t access stuff when its not rendered in the DOM via getElementById() or something but in your case you try to access data from the minimongo (your local mongodb version in the browser) not the DOM so your template is not important here.
Just wait until your subscribtion is ready that your minimongo own all the data with the onReady callback in your subscribtion call and fire your functions.
https://docs.meteor.com/api/pubsub.html#Meteor-subscribe
callbacks (Function or Object).
Optional. May include onStop and onReady
callbacks. If there is an error, it is passed as an argument to
onStop. If a function is passed instead of an object, it is
interpreted as an onReady callback.