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.
Related
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.
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;
}
});
I am working on an edit form that has two paths. One is when the user clicks a "New" button, the other is when they click "Edit".
When they click "New", the code sets a form_id Session var to null and a client_id session variable to null, then does a Router.go('formEdit') to load the formEdit template/route.
In the formEdit.js, I do a reactive Template helper (I think that's what they are called, but anyway) like so:
Template.formEdit.form = function() {
var form;
if (Session.equals('form_id', null)) {
// Create empty form
form = {
title: null,
client_id: Session.get('client_id'),
header_fields: [],
form_fields: []
};
} else {
// Load form
form = Forms.findOne({_id: Session.get('form_id')});
}
return form;
}
Basically I check if the form_id was set or not, if so I load it from the Forms collection, if not I create a blank one. I thought this would be pretty simple, really.
The problem is that the created/found form object does not behave in a "reactive" way. If I add header_fields or form_fields the subsequent template code never updates. Both are in a {{#each}} like so:
<template name="formEdit">
...
{{#each header_fields}}
{{> headerFieldOutput}}
{{/each}}
...
{{#each form_fields}}
{{> formFieldOutput}}
{{/each}}
</template>
How do I make it such that I can push header_fields and form_fields onto the form and have the underlying template reactively update the {{#each}}'s?
I think you're going about it a little differently than what the reactive programming methodology in Meteor is expecting.
You're putting the 'display' logic in your template helper, rather than using the template scaffolding itself to do it.
So, declare a very simple template helper, something like this:
Template.formEdit.form = function () {
return forms.findOne(Session.get("form_id"));
};
And then, in your template scaffolding have something like this:
{{#if form}}
{{#with form}}
{{#each header_fields}}
etc...
{{/with}}
{{#else}}
[[insert your blank form scaffolding in here]]...
{{/if}}
Then, as you set your Session form_id variable, you can set it to null to invoke the {{#else}} portion.
There are more details than this (logic in the form submit click handler to identify if you are performing an update or an insert, for example) but hopefully you get the gist of it from this.
You should try to gain a better understanding about how cursors and reactive computations work, as it will help you better understand how to best use the reactive methodology. A good starting place is the parties example (watch the video and walk through the code manually). It's similar to what you're doing, and shows a good way of building your templates for when you don't have a 'selected' object.
Hope this helps!
Using Meteor, I am trying to loop through and display a list of notes from a database with an option to delete each note.
Here is the HTML (using Handlebars.js)
<template name="Notes">
{{#each NoteArr}}
<div class="Note">
<h2>{{Title}}</h2>
<p>{{Body}}</p>
<span class="deleteNote">Delete</span>
</div>
{{/each}}
</template>
And here is the client Javascript
Template.Notes.events = {
"click .deleteNote" : function(){
noteID = $('.deleteNote').parent().attr("id");
Notes.remove({ID:noteID});
}
};
This grabs the first instance of .deleteNote, so unless I'm trying to delete the first one, that won't help. How can I grab the parent of the particular instance of .deleteNote that was clicked, not just the first one it finds?
The reason why the first element is deleted is.. in your .click event, you are accesssing the div directly as $('.deleteNote').parent() which grabs the first node in the html which has a class .deleteNode.
Now to remove the specific notes, from the collection: Every document in the collection has a unique _id attribute which is generated automatically. assign that unique _id of the document to the span element as <span id= "{{_id}}" class="deleteNote">Delete</span>.
So the cilck event will look like:
Template.Notes.events = {
"click .deleteNote" : function(e){
var noteID = e.currentTarget.id;
Notes.remove({_id:noteID});
}
};
And the template will look like:
<template name="Notes">
{{#each NoteArr}}
<div class="Note">
<h2>{{Title}}</h2>
<p>{{Body}}</p>
<span id= "{{_id}}" class="deleteNote">Delete</span>
</div>
{{/each}}
</template>
Untested code, but hope this will help solving your issue.
The _id of a note is stored in 'this' as well. In addition, the remove function accepts '_id' as a string. So this should work as well:
Template.Notes.events = {
'click .deleteNote': function(){ return Notes.remove(this._id)}
}
A few benefits here. Less querying the DOM for information. Less jQuery. Fewer lines of code to think about. Cleaner templates.
Meteor promises reactive updates, so that views are auto-updated when data changes. The included leaderboard example demonstrates this. It runs fine when I test it: data is updated across several browsertabs in different browsers, as expected.
All set and go, I started coding with meteor and progress was being made, but when I tested for reactive updates across browertabs, I noticed that only after a short while the updates across tabs stopped.
I boiled down the problem to the following code, based on a new empty meteor project:
updatebug.html
<head>
<title>updatebug</title>
</head>
<body>
{{> form}}
</body>
<template name="form">
<form onsubmit="return false;">
{{#each items}}
{{> form_item }}
{{/each}}
</form>
</template>
<template name="form_item">
<div>
<label>{{name}}
<input type="text" name="{{name}}" value="{{value}}">
</label>
</div>
</template>
updatebug.js:
Items = new Meteor.Collection("items");
if (Meteor.is_client) {
Template.form.items = function () {
return Items.find();
};
Template.form_item.events = {
'blur input': function(e) {
var newValue = $(e.target).val();
console.log('update', this.name, this.value, newValue);
Items.update({_id: this._id}, {$set: {value: newValue}});
},
};
}
if (Meteor.is_server) {
Meteor.startup(function () {
if (Items.find().count() === 0) {
Items.insert({name: 'item1', value: 'something'});
}
});
}
Run in multiple browsertabs, start changing the value of the input in one tab. The other tabs will reflect the change. Goto the next tab and change the value. Repeat a couple of times.
After a while, no more updates are received by any other tabs. It seems that once a tab has changed the value, it does not receive/show any more updates.
Differences compared to the leaderboard example (since it's very similar):
The leaderboard uses no form controls
The leaderboard example does an increment operation on update, not a set
I am about to file a bug report, but want to be sure I am not doing anything stupid here, or missing an essential part of the Meteor Collection mechanics (yes, autopublish package is installed).
The issue here is input element preservation. Meteor will preserve the input state of any form field with an id or name attribute across a template redraw. The redraw is preserving the old text in your form element, because you wouldn't want to interrupt another user typing in the same field. If you remove the name attribute from the text box, each tab will update on blur.
In fact, I'm not sure why the first update works in your example. That may actually be the bug!
You can see it's not a data problem by opening the console in each browser. On each blur event you will get an updated document in every open tab. (Type Items.find().fetch())