I need to set a variable or array in meteor JS which whenever changes. Wherever it is used on the page changes.
So far I have tried to set values in session.
let in = Session.get("in");
and this in HTML. The following works fine. This changes whenever it detects a change in array
{{#each in}}
<span class="selectable-tags"> {{this}} </span>
{{/each}}
But whenever I try to add these tags to other div using following. Then the ones added to other div does not change.
"click .selectable-tags"(e, t) {
// sets the tags inside the Method box on click
var el = e.target.cloneNode(true);
el.setAttribute('contenteditable', false);
document.querySelector('[contenteditable]').appendChild(el); },
using meteor with blaze UI. This can be used as reference link
Edit: Session.get or set is given for reference . This was to tell that these values are changing as they on any event triggered wherever set.
You need to add a helper that returns the session variable and show the helper in your html code :
Template.yourtemplate.helpers({
inHelper: ()=> {
return Session.get('in');
}
)}
And in html :
<div>{{inHelper}}</div>
Every modification on in by Session.set('in', newValue) will change your HTML.
Related
I have the following templates (.html) with their respected managers (.js files):
adminManageCategories
adminAddCategory
adminUpdateCategory
Consider the following:
<template name="adminManageCategories">
{{#each category}}
<div class="clickme">{{title}}</div>
{{/each}}
{{> adminUpdateCategory}}
</template>
Notice the {{> adminUpdateCategory}} is outside of the iteration. This is also a form, and I want to keep it on the same page.
And admin_manage_categories.js
Template.adminManageCategories.events({
"click .clickme": function(event) {
event.preventDefault();
console.log(this._id);
}
});
Notice the console.log() function, which works, as the template manager is smart enough to know the ID of the item that was clicked.
What I want to do is load this items values into the form when clicked. My example above is slim, but in my real data I have a title, sort order, among other things.
So my question is, what is the proper way to pass the _id from the adminManageCategories template to the adminUpdateCategory template, which is the form?
I can hack at this with JavaScript and make things happen, but I think I'm missing a "Meteor way" of doing things.
You need to use a ReactiveVar to store the currently clicked item.
First you need to run meteor add reactive-var, as it's not a package added by default in a standard meteor web app.
JS:
Template.adminManageCategories.created=function(){
// instantiate the reactive-var in the created callback
// we store it as a property of the template instance
this.currentItemId=new ReactiveVar(null);
};
Template.adminManageCategories.helpers({
// this helper reactively returns the currently clicked item
currentItem:function(){
// retrieve the reactive-var from the template instance...
var currentItemId=Template.instance().currentItemId.get();
// ...to fetch the correct collection document
return Items.findOne(currentItemId);
}
});
Template.adminManageCategories.events({
"click .clickme": function(event,template) {
event.preventDefault();
// assign the correct item id to the reactive-var attached to this template instance
template.currentItemId.set(this._id);
}
});
HTML:
<template name="adminManageCategories">
{{#each category}}
<div class="clickme">{{title}}</div>
{{/each}}
<p>Current item title is : {{currentItem.title}}</p>
{{! pass the currentItem as a parameter to your child template this will be
accessible as {{item}} in the HTML and "this.item" in JS helpers or
"this.data.item" in created/rendered/destroyed callbacks}}
{{> adminUpdateCategory item=currentItem}}
</template>
EDIT:
When I initialize the reactive-var in the created callback, I set it to null, this means that until one item is clicked, the helper will return null too and when you'll try to access this.item._id in the adminUpdateCategory this will fail.
The simplest way to solve this issue is maybe to not initialize the variable to null but to the first item in the collection.
Template.adminManageCategories.created=function(){
var firstItem=Items.findOne({},{
sort:{
sortedField:1
}
});
this.currentItemId=new ReactiveVar(firstItem && firstItem._id);
};
There may still be a case when you have 0 items in the collection, so you'll probably end up having to guard against the existence of the item in the JS.
Template.adminUpdateCategory.helpers({
itemProperty:function(){
return this.item && this.item.property;
}
});
In my meteor app I need to load an array of items corresponding to the item clicked.As I'm new to meteor, I'm held up here.Here is my code.
Template.templatename.events({
'click .showdiv' : function()
{
Template.templatename.vname = function () {
return Db.find();
}
}
Can I set the variable vname dynamically by this code ? This is not working for me.
I think you're misunderstanding the notion of reactivity. A reactive data source will cause any functions which depend on it (including helpers) to rerun when its value is changed, which seems to be the behavior you're looking for here. Instead, you're rewriting the helper function itself every time an item is clicked, which kind of defeats the object of Meteor's reactive data model. Session variables could help:
Template.templatename.events({
'click .showdiv' : function() {
Session.set('vname', Db.find());
}
});
Template.templatename.vname = function () {
return Session.get('vname');
}
If you use an {{#each vname}} block in the templatename template, it will automatically update with the results of the Db.find() query when a .showdiv is clicked. If all you want to do is show the result of that query regardless of whether a click has been registered it would be as simple as:
Template.templatename.vname = function () {
return Db.find();
}
Note that it's still not clear exactly what data you're trying to populate here since the query will return a cursor (which is fine, but you need to loop through it using {{#each ...}} - use findOne if you only want one item), and its contents aren't going to depend on anything intrinsic to the click event (like which .showdiv you clicked). In the former example it will however fail to show anything until the first click (after which you would have to reset with Session.set('vname', null) to stop it showing anything again).
I have a sortable list.
<template name="the_playlist">
{{#each main_list}}
<li id="{{index}}" class="list_element">
<div class="next_song">...</div>
<div class="destroy">...</div>
<div class="element_style">{{song_title}}</div>
</li>
{{/each}}
</template>
And this is the main_list that it prints from.
Template.the_playlist.main_list = function(){
//if ret is valid, it will have a songs member
var ret = Links.find().fetch()[0];
if (typeof ret == 'undefined'){
ret = []
}
else {
ret = Links.find().fetch()[0].songs;
}
return ret;
}
And I am using the sortable plugin and more importantly its update callback which updates everytime the user changes a position the list or an element is added to the list.
$(function() {
$( "#playlist" ).sortable({
update: function(){
Template.list.updateList(); //MODIFIES DB CONTENTS, AND MAIN_LIST's VALUES CHANGE
}});
$( "#playlist" ).disableSelection();
});
*The problem: * If a page already has list elements when it's loaded, for one time only, I would like to add a class that hides (.addClass("hide")) each of the next_song elements that are on the page at that time. This *will work only until main_list changes* by a call to Template.list.updateList above, after which automagically, the added class will disappear - most likely due to the re-rendering that is occuring since the main_list depends on the db changes.
The following in the JQuery snippet I use to try and accomplish this.
$("#playlist li .next_song").each(function(){
$(this).addClass("hide_song");
})
Here is a demo. Try plugging in the above JQUery code into the console. and then move the list elements around to see the problem.
Can you not just determine whether that will be the case in a helper function?
Template.the_playlist.helpers({
'list_elements_exist': function() {
return (!!$('#playlist li').length);
}
}
Then you can just insert the logic straight into the template:
<div class="next_song{{#if list_elements_exist}} hide_song{{/if}}">...</div>
To be honest, I'm not 100% sure that this will float with reactivity depending on the structure of your app. If it doesn't work properly, I'd introduce a new session boolean, list_elements, the value of which is returned by the helper function above. It should be fairly easy to update its value in event handlers or created callbacks to keep it tracking whether there are any items in the list or not, and this will guarantee the list renders as required regardless of other dependencies changing.
I'm struggling with an issue that I will explain giving a simple demo.
There's following very simple document in People Collection.
{
"_id" : "vxmLRndHgNocZouJg",
"fname" : "John" ,
"nicks" : [ "Johnny" , "Jo"]
}
Now let's consider following templates. Basically I display username and a list of nicknames with input field for adding more nicknames.
<head>
<title>test</title>
</head>
<body>
{{> name}}<br/>
{{> nicks}}
</body>
<template name="name">
<input type="text" value="{{fname}}"/>
</template>
<template name="nicks">
{{#each nicks}}
<div>{{this}}</div>
{{else}}
no nicks yet
{{/each}}
<input type="text" name="nicks"/>
<input type="submit"/>
</template>
My client javascript code is as follows:
Template.name.fname = function() {
return People.findOne({"fname" : "John"},{
transform : function(doc) {
return doc.fname;
}
});
}
Template.name.rendered = function() {
console.log('Template "name" rendered!');
}
Template.nicks.nicks = function() {
var john = People.findOne({"fname" : "John"});
if(john) return john.nicks;
}
Template.nicks.events({
'click input[type="submit"]' : function () {
var johnId = People.findOne({"fname" : "John"})._id; // demo code
People.update(johnId,{
$addToSet : {
nicks : $('input[name="nicks"]').val()
}
})
}
});
My problem is that after adding nickname (update of nicks field in a document) template name is re-rendered (I know because I console.log it). When I query People collection to provide data for name template I use transform option so changes in nicks field shouldn't have impact on name template.
Meteor docs supports this:
Cursors are a reactive data source. 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.
Why template name is re-rendered then?
The template is re-rendered because you change the People collection.
When you alter the People collection, Meteor automatically assumes that everything that it provides data to needs to be recalculated. (Which your name template does via Template.name.fname.
Even though you transform the output of the cursor, the People collection has changed in some way. The query is done before the transform is used, in other words, its not the transform that is looked at but the whole collection.
Meteor thinks that perhaps your document with {'fname':'John'} may have some other field that might have changed and it needs to requery it to check (which the nicks field has been altered). The transform is then applied after the requery.
Your HTML might not actually change at this point, only if the cursor returns something different will the html be changed.
If it becomes an issue in any scenario (i.e forms being cleared or DOM being changed when it shouldn't be) you can use the {{#isolate}} {{/isolate}} blocks to ensure that only everything inside them is re-rendered and nothing outside.
I'm very new to meteor, so apologies if I'm missing something very basic here.
I thought it would be fun to create a very simple textpad style app to check out meteor. I took the todo app and changed the data structures to be 'folders' and 'docs' rather than 'lists' and 'todos', so I have a list of folders and when you click on the folder you get a list of the documents in that folder.
I've then added some code to show the 'content' attribute of a single 'doc' when one of the docs in the list is clicked.
I'm using ace to add some pretty print to the content of the doc (https://github.com/ajaxorg/ace). I've set ace up to work with a hidden textarea containing the plaintext version of my document, and the editor object takes this text and pretty prints it.
The problem with ace is that I don't want the template containing the ace editor to be replaced every time the contents of the doc changes (as it takes half a second to reinitialise, which is a crappy experience after every character is typed!). Instead, I want to update the textarea template and then use the ace API to tell the editor to update it's input based on what is in the textarea.
Now, this is probably the wrong way to approach the problem, but I've ended up using two templates. The first contains a textarea containing doc.contents, which is reactive to the underlying model:
<template name="doc_content">
<textarea name="editor">{{content}}</textarea>
</template>
The second one contains the 'editor' div which ace uses to display the pretty printed text.
<template name="doc_init">
<div id="editor"></div>
</template>
The idea is that the first template will update every time the user types (on all clients), and the second template is only ever re-loaded for each new doc we load.
Template.doc_content.content = function() {
var doc_id = Session.get('viewing_itemname');
if (!doc_id) {
return {};
}
var doc = Docs.findOne({_id:doc_id});
if (doc && doc.content) {
// #1 Later
var editor = Session.get('editor');
if (editor) {
editor.getSession().setValue(doc.content);
}
return doc.content;
} else {
return '';
}
};
When you enter text into the editor div I make a call to Docs.update(doc_id, {$set: {content: text}});, which updates the value in the textarea on each client. All good so far.
editor.getSession().on('change', function(){
var text = editor.getSession().getValue();
Docs.update(doc_id, {$set: {content: text}});
});
What I want to do, for all clients other than the client which made the change, is to subscribe to the change for that doc and call editor.getSession().setContent() with the text which has just been changed, taking the text from the textarea and using it to fill the editor.
I've tried to do this by making that call from the template containing the textarea (as this changes whenever the doc is updated - see #1 above). However, this puts the clients into an infinite loop because changing the value in the editor causes another call to Docs.update.
Obviously this doesn't happen when you render a template, so I'm assuming there's some magic in meteor which can prevent this happening, but I'm not sure how.
Any thoughts?
TIA!
There's a lot to absorb in your question, but if I understand correctly, you might simply be after Deps.autorun:
Deps.autorun(function () {
var doc_id = Session.get('viewing_itemname');
if (!doc_id) {
return {};
}
var doc = Docs.findOne({_id:doc_id});
// do stuff with doc
});
Deps.autorun is really useful in that it will get re-run if any of its
dependencies change. These dependencies are limited to those that are "reactive"
such as Collections and Sessions, or anything that implements the reactive API.
In your case, both Session.get and findOne are reactive so if their values
change at all, Deps.autorun will run the function again.