I am trying to be as lazy loading as possible,
But, I am puzzle on how to start, here is my "sequenced comprehension":
Objective: Create a contacts page with contacts existing on the server
Step1.0: To use the router: the <div id="contacts"> must exists to trigger a rule, so I stepped back to (Step0.9),
Step0.9: Created this div in the body. Fine, the router find the #contacts, Oh, but this is a view, ok, stepped back to (Step0.8).
Step0.8: Erase the div created in the body and replace it by a view instead:
contactsView = Backbone.View.extend
tagName: 'div',
id: 'contacts'
To be lazy loading, this view should only be created when the #contact is trigger in my router table, but I just removed it from by body, it does exist anymore, I am back to Step1.0 ???
Some tutorials found, shows global variable settings... Please, how the general scenario using a router, a view, their models, and collection should proceed (no code is necessary for an answer, just one line for each steps) ?
I know there can be multiples ways, but what is the most common backbone step strategy to create elements.
Thanks in advance.
I'm not 100% sure I understood you correctly. If I didn't please let me know in the comments.
There seems to be some confusion in your question regarding the usage of Backbone.Router in general. When the router maps a route to URL fragment #contacts, that has nothing to do with a DOM element with the id #contacts. The hash sign simply happens to be the identifier for an URL fragment and id CSS selector, but that's where the similarity ends.
Typically my router looks something like this:
var AppRouter = Backbone.Router.extend({
routes: {
contacts: "contactList"
},
contactList: function() {
var contacts = new ContactCollection();
var view = new ContactListView({collection:contacts});
view.render().$el.appendTo("#contacts");
}
});
Notice that the #contacts element doesn't need to be called that. You can call it #pony, or you can render the view directly to the document body if you want.
So in these terms the workflow is:
Router gets hit
Collection is initialized
View is rendered
Usual way i do is
Have the div#contacts loaded within body
Router maps the #contacts to the method showContacts in the router
showContacts creates the view, attaches it to the desired div
var view = new contactsView();
$('#contacts').empty().append(view.el);
view.render();
You need not define the id in the definition of contactsView
Related
Within the onBeforeRendering() function of a view how should I determine if a specific node is present in the model and modify the model to include the node if not? This question is about lazy loading of data to the model for data that will be infrequently accessed by users but would have a performance penalty if loaded with initial model data.
My use case has a list page leading to a detail page for whatever item in the list the use clicks. On the detail page is a set of tabs which expose sub-details related to the selected detail. Specifically a long text description of a the brief for a task.
The tab control leads via manifest.json style routing to display a view in the tabs content area.
This is my current working code which is within the onBeforeRendering event of the view controller:
onBeforeRendering: function(oEvent){
var sPath = this.getView().getBindingContext("Projects").getPath(); // something like /task/6
console.log('Path='+sPath)
var oModel = this.getView().getModel("Projects");
var oTask = oModel.getProperty(sPath + "/brief");
if (oTask) { // looks like /brief exists so must already have loaded the brief
// nothing to do
console.log('Use existing data')
}
else { // /brief not yet present so we need to load it up
console.log('Load new data')
oModel.setProperty(sPath + "/brief", "This is the brief...") // replace with loaddata() from server, use attachRequestCompleted to call function to modify model.
}}
Question - is this the correct approach?
Edit: Based on discussion in this question I modified my code to use an event that fires per display of the view. onBeforeRendering turned out to run without much apparent predictability - which I am sure it has but in any case I wanted a one-per-display event. Also, I fleshed out the code further but retained the basic structure and it appears to do what I wanted.
This is a valid approach. But you should think aboute following use case: What happens if the data you loaded have been changed at the backend? The JSONModel does not give you any support here as it acts dumb data store only.
I have sap.ui.table.Table which rows are bound to an JSONModel.
var oListModel = new sap.ui.model.json.JSONModel();
//oTable created here (sap.ui.table.Table)
oTable.setModel(oListModel);
oTable.bindRows("/");
When the table is rendered, i.e. the DOM is created for this table, i need to reference to the DOM to pass the DOM elements (table rows) to a library which will make them draggable.
My problem is: How do i know when the DOM for the table is created after the model has been changed and the table is rerendered? I didnt find any listener. The view controller's listener onAfterRendering() didn't help me.
The model is filled with data after a XMLHTTPRequest is successful. When i set the model in the success handler of the xht request and try to access the DOM elments directly afterwards they don't exist yet.
Thank you for your help!
You can add an event delegate
var oMyTable = new sap.ui.table.Table();
oMyTable.addEventDelegate({
onAfterRendering: function() {
$table = this.getDomRef() ....
}
});
a better way is to extend the control see Using addDelegate to extend a control to use third party functionality
UPDATE
the example in that blog doesn't work anymore fixed here
I had a similar issue recently where i had to access an element after a smartform (where the element is present) rendered onto the view. I posted my query here as well as my final solution (based on the accepted answer of #Dopedev). I am using XML views - including nested XML views - here however and the onAfterRendering didn't help for me as well.
I guess you could look at this solution - like it's mentioned in the accepted answer, it may not be an optimal solution, but it sure works. In my case there is not much of a performance issue with the binding of the DOMNodeInserted since it is being called in the onAfterRendering of the nested view that consists of only the smartform with an immediate unbinding upon finding.
The condition if (id === "yourtableid") { } should be enough to identify and pass on. Since you have a table and thus several child nodes, unbinding is imperative at this point.
Mutation Observer is the preferred method but i guess you may need to check the browser compatibility table at the end of the page to see if it matches your requirements. There is an example here. I have used Mutation Observer (outside of a SAPUI5/openUI5 environment) earlier and found it very convenient(and performant) to listen to DOM insert events. In fact the sap.ui.dt package consists of MutationObserver.js
Say I wrote a blog app in Sails.js.
On every page in this app, there is a sidebar widget called "Recent Posts", where it lists the titles of the 5 most recent posts and clicking on them takes you to the post in question.
Because this sidebar widget is present on every page, it should be in layout.ejs. But, here we have a conflict - dynamic content is only supposed to be pulled from the database in the controller action for rendering a specific view.
This dynamic content isn't for a specific view, it's for the whole site (via layout.ejs).
By the conventions that I understand, I'd have to get that dynamic content data for the sidebar widget in every controller action that renders a view (otherwise I would get an undefined error when I attempt to call that local in my layout.ejs file).
Things I've tried / considered:
Load that dynamic content in every controller action that renders a view (this solution is very bad) and calling that dynamic content in layout.ejs as if it were a local for the specific view. This works fine, but goes against D.R.Y. principles and quite frankly is a pain in the ass to have to run the same query to the database in every controller action.
As per another similar stackoverflow question, create a new config (E.G. config/globals.js), load my dynamic content from my database into that config file as a variable, and then calling sails.config.globals.[variable_name] in my layout.ejs file. This also worked, since apparently config variables are available everywhere in the application -- but it 's a hacky solution that I'm not a fan of (the content I'm loading is simply the titles and slugs of 5 recent posts, not a "global config option", as the solution implies).
Run the query to get the dynamic content inside the .EJS file directly between some <% %> tags. I'm not sure if this would work, but even if it did, it goes against the separation of concerns MVC principle and I'd like to avoid doing this if at all possible (if it even works).
As per a lengthy IRC discussion # http://webchat.freenode.net/?channels=sailsjs, it was suggested to create a policy and map that policy to all my controllers. In that policy, query the database for the 5 most recent posts, and set them to the req.recentposts. The problem with this solution is that, while the recent posts data will be passed to every controller, I still have to pass that req.recentposts data to my view -- making it so I still have to modify every single res.view({}) in every action. I don't have to have the database query in every action, which is good, but I still have to add a line of code to every action that renders a view... this isn't D.R.Y. and I'm looking for a better solution.
So, what is the proper solution, without needing to load that dynamic content in every controller action (a solution that adheres to D.R.Y. is what I'm lookng for), to get some dynamic content available to my layout.ejs file?
In folder /config you should create a file express.js and add something like that:
module.exports.express = {
customMiddleware: function(app){
app.use(function(req, res, next){
// or whatever query you need
Posts.find().limit(5).exec(function(err, posts){
res.locals.recentPosts = posts;
// remember about next()
next();
});
});
}
}
Then just make some simple loop in your view:
<% for(var i=0; i<recentPosts.length; i++) { %>
<% recentPosts[i].title %>
<% } %>
Here are some links to proper places in documentation:
https://github.com/balderdashy/sails-docs/blob/0.9/reference/Configuration.md#express
and
https://github.com/balderdashy/sails-docs/blob/0.9/reference/Response.md#reslocals
I found out another way to do this. What I did was to create a service that could render .ejs files to plain html by simply taking advantage of the ejs library already in sails. This service could either be invoked by the controller, or even passed as a function in the locals, and executed from within the .ejs. The service called TopNavBarService would look like:
var ejs = require('ejs');
exports.render = function() {
/* database finds goes here */
var userInfo = {
'username' : 'Kallehopp',
'real_name' : 'Kalle Hoppson'
};
var html = null;
ejs.renderFile('./views/topNavBar.ejs', {'locals':userInfo}, function(err, result) { html = result; });
return html;
}
In the constroller it could look like:
module.exports = {
testAction: function (req, res) {
return res.view('testView', {
renderNavbar: TopNavBarService.render // service function as a local!
});
}
};
This way you can create your customized ejs-helper that could even take arguments (although not shown here). When invoked, the helper could access the database and render a part of the html.
<div>
<%- renderNavbar() %>
</div>
Just wondering if anyone knows a good/simple approach using Durandal to disposing of or re-initializing a viewmodel once it becomes invalid?
I have a registration form that I could 're-initialize' manually after a user has completed the form and registered successfully, but I'd prefer to just dispose of it so that Durandal creates a new registraion view/view model when that particular route is accessed again.
If your viewmodel module returns a function rather than an object, it will create a new one each time rather than reusing the 'singleton' object. See the Module Values section of Creating a Module.
Updated link for the Durandal Module constructor function information: Module Values
You can split the difference:
var cache;
var ctor = function () {
if (cache) return cache;
// init logic
cache = this;
}
Just replace the if(cache) check with whatever "do I need a new thing or not" logic you like.
If you're using routing, simply redirect the user to an instance-based module (one that returns a constructor function). The user will most likely click or touch a button that signifies that he is done with the registration form. That would be the redirect action.
If you're using composition, you would still create an instance-based module. Then, you would use dynamic composition to swap it in once the user signified he was done with the registration form.
Dynamic composition is where the view and/or model attributes on a Durandal composition are, themselves, observables, referencing something like the following in the viewModel:
this.currentView = ko.observable('');
this.currentModel = ko.observable('');
Then, in your HTML:
<div>
<div data-bind="compose: {view: currentView(), model: currentModel())"></div>
</div>
When the user clicks "Done", or something to that effect, functions on your viewModel might look something like:
ctor.prototype.done = function () {
this.setCurrentView('viewmodels/registrationForm.html');
this.setCurrentModel('viewmodels/registrationForm.js');
}
ctor.prototype.setCurrentView = function (view) {
this.currentView(view);
}
ctor.prototype.setCurrentModel = function (model) {
this.currentModel(model);
}
Either one of the approaches above will create the registrationForm only when it's needed.
With Durandal 2.0, you can use the deactivate callback within the composition lifecycle. Here is some documentation http://durandaljs.com/documentation/Hooking-Lifecycle-Callbacks
I know there is .on and .live (deprecated) available from JQuery, but those assume you want to attach event handlers to one ore more events of the dynamically added element which I don't. I just need to reference it so I can access some of the attributes of it.
And to be more specific, there are multiple dynamic elements like this all with class="cluster" set and each with a different value for the: title attribute, top attribute, and left attribute.
None of these jquery options work:
var allClusters = $('.cluster');
var allClusters2 = $('#map').children('.cluster');
var allClusters3 = $('#map').find('.cluster');
Again, I don't want to attach any event handlers so .on doesn't seem like the right solution even if I were to hijack it, add a bogus event, a doNothing handler, and then just reference my attributes.
There's got to be a better solution. Any ideas?
UPDATE:
I mis-stated the title as I meant to say that the elements were dynamically added to the DOM, but not through JQuery. Title updated.
I figured it out. The elements weren't showing up because the DOM hadn't been updated yet.
I'm working with Google Maps and MarkerClustererPlus to give some more context, and when I add the map markers using markerclustererplus, they weren't available in the javascript code following the add.
Adding a google maps event listener to my google map fixed the problem:
google.maps.event.addListener(myMarkerClusterer, 'clusteringend', function () {
// access newly added DOM elements here
});
Once I add that listener, all the above JQuery selectors and/or methods work just fine:
var allClusters = $('.cluster');
var allClusters3 = $('#map').find('.cluster');
Although this one didn't, but that's because it only finds direct decendants of parent:
var allClusters2 = $('#map').children('.cluster');
Do what you need to do in the ajax callback:
$.ajax(...).done(function (html) {
//append here
allClusters = $('.cluster');
});
If you want them to be separate, you can always bind handlers after the fact, or use $.when:
jqxhr = $.ajax(...).done(function (html) { /* append html */ });
jqxhr.done(function () { allClusters = $('.cluster') });
$.when(jqxhr).done(function () { /* you get it */ });
If these are being appended without ajax changes, then just move the cluster-finding code to wherever the DOM changes take place.
If that's not an option, then I guess you would just have to check on an interval.