I have a bot running an infinite loop in rails. I want to have things in the code periodically print to the view page as its running. Since I am having the bot run on an infinite loop I need some way to asynchronously load the page that will output the periodic updates of its actions. What is the best way to do this in rails?
Let me cover 3 different approaches you can take:
Javascript refresh every period of time
Sockets
Prebuild dashboards
Javascript refresh would be simply adding:
setTimeout(function(){
window.location.reload(1);
}, 5000);
or
<meta http-equiv="refresh" content="5; URL=http://www.yourdomain.com/yoursite.html">
as discussed on the question located at:
How to reload page every 5 second?
For websockets you can do a direct connection. We use https://github.com/websocket-rails/websocket-rails
for our production environment.
Finally for a dashboard you may want to consider:
https://github.com/gottfrois/dashing-rails
It is phenomenally easy to setup and get going. It does pump the data right to the client but allows you to skip a lot of the nitty gritty and just get running. As a warning, we had issues mixing this with other items and that is why we do not use it on production.
I have a proof-of-concept that is thoroughly and utterly broken here:
http://jsfiddle.net/floyd_may/FAmxj/
I'm hoping the intent behind this is evident. Basically, I want to use #editPage to edit elements on #mainPage one at a time. However, as soon as you click the 'Back to Main Page' button, the main page is empty.
Can I get some guidance here as to how to make this work?
Try using the pageinit event instead of pagebeforeshow: http://jsfiddle.net/FAmxj/11/
With pagebeforeshow, multiple models are bound to #mainpage.
One action of one of my controllers needs to generate(redirect/render) two separate views simultaneously and show both the pages to the client. It will be like when the user submits his info, the page will redirect to a new page with a list. At the same time another page needs to pop up in a new window containing some additional info (user would print this page). I know, I can resolve the issue with a single page, but I was wondering whether there is any ways to produce two separate pages/windows simultaneously from a single controller action.
Thanks in anticipation
The simple answer is NO. Grails isn't doing anything magical. It's still constrained to normal HTTP request/response lifecycle. A single request gets a single response. What you're asking for sounds like you want grails to be able to generate 2 responses for a single HTTP request which is impossible. The response is either a page for the browser to render or it's a redirect message for the browser to go to another URL.
You could write your action that it can handle normal and ajax requests. See the docs here:
Responding to both Ajax and non-Ajax requests
Then you could generate your "normal" view. After that you call the same action by using ajax on the client side and load the data for your pop up page.
why not use a <script>window.open()</script> in your main view in order to open the popup?
I'm looking on how exactly I can show a "loading element" while the page is first requested. Most examples I find, explain on how to show a "loading element" on an Ajax.BeginForm or Ajax.ActionLink...
What I'm trying to do is having a couple of dashboards.
When the user requests the page, the dashboards are shown immediately, but the data is still being loaded.
While the data is being loaded, a "loading element" should appear in the dashboard.
So, some sort of Ajax.RenderPartial, but that does not exist :)
In this case you could show the loading element immediately when the page is first requested along with the dashboards and hide it later when those dashboards are finished loading. There's the endRequest event you could subscribe to.
I'm making my way into web development and have seen the word postback thrown around. Coming from a non-web based background, what does a new web developer have to know about postbacks? (i.e. what are they and when do they arise?)
Any more information you'd like to share to help a newbie in the web world be aware of postbacks would be most greatly appreciated.
The following is aimed at beginners to ASP.Net...
When does it happen?
A postback originates from the client browser. Usually one of the controls on the page will be manipulated by the user (a button clicked or dropdown changed, etc), and this control will initiate a postback. The state of this control, plus all other controls on the page,(known as the View State) is Posted Back to the web server.
What happens?
Most commonly the postback causes the web server to create an instance of the code behind class of the page that initiated the postback. This page object is then executed within the normal page lifecycle with a slight difference (see below). If you do not redirect the user specifically to another page somewhere during the page lifecycle, the final result of the postback will be the same page displayed to the user again, and then another postback could happen, and so on.
Why does it happen?
The web application is running on the web server. In order to process the user’s response, cause the application state to change, or move to a different page, you need to get some code to execute on the web server. The only way to achieve this is to collect up all the information that the user is currently working on and send it all back to the server.
Some things for a beginner to note are...
The state of the controls on the posting back page are available within the context. This will allow you to manipulate the page controls or redirect to another page based on the information there.
Controls on a web form have events, and therefore event handlers, just like any other controls. The initialisation part of the page lifecycle will execute before the event handler of the control that caused the post back. Therefore the code in the page’s Init and Load event handler will execute before the code in the event handler for the button that the user clicked.
The value of the “Page.IsPostBack” property will be set to “true” when the page is executing after a postback, and “false” otherwise.
Technologies like Ajax and MVC have changed the way postbacks work.
From wikipedia:
A Postback is an action taken by an
interactive webpage, when the entire
page and its contents are sent to the
server for processing some information
and then, the server posts the same
page back to the browser.
Expanding on the definitions given, the most important thing you need to know as a web-developer is that NO STATE IS SAVED between postbacks. There are ways to retain state, such as the Session or Viewstate collections in ASP.NET, but as a rule of thumb write your programs where you can recreate your state on every postback.
This is probably the biggest difference between desktop and web-based application programming, and took me months to learn to the point where I was instinctively writing this way.
Postback happens when a webpage posts its data back to the same script/dll/whatever that generated the page in the first place.
Example in C# (asp.net)
...
if (!IsPostback)
// generate form
else
process submitted data;
Web developement generally involves html pages that hold forms (<form> tags). Forms post to URLs. You can set a given form to post to any url you want to. A postback is when a form posts back to it's own page/url.
The term has special significance for ASP.Net WebForms developers, because it is the primary mechanism driving a lot of the behavior for a page — specifically 'event handling'. ASP.Net WebForms pages have exactly one server form which nearly always posts back to itself, and these postbacks trigger execution on the server of something called the Page Lifecycle.
The term is also used in web application development when interacting with 3rd party web-service APIs
Many APIs require both an interactive and non-interactive integration. Typically the interactive part is done using redirects (site 1 redirects a user to site 2, where they sign in, and are redirected back). The non-interactive part is done using a 'postback', or an HTTP POST from site 2's servers to site 1's servers.
When a script generates an html form and that form's action http POSTs back to the same form.
Postback is essentially when a form is submitted to the same page or script (.php .asp etc) as you are currently on to proccesses the data rather than sending you to a new page.
An example could be a page on a forum (viewpage.php), where you submit a comment and it is submitted to the same page (viewpage.php) and you would then see it with the new content added.
See: http://en.wikipedia.org/wiki/Postback
Postback refers to HTML forms. An HTML form has 2 methods: GET and POST. These methods determine how data is sent from the client via the form, to the server. A Postback is the action of POSTing back to the submitting page. In essence, it forms a complete circuit from the client, to the server, and back again.
A post back is anything that cause the page from the client's web browser to be pushed back to the server.
There's alot of info out there, search google for postbacks.
Most of the time, any ASP control will cause a post back (button/link click) but some don't unless you tell them to (checkbox/combobox)
Yet the question is answered accurately above, but just want to share my knowledge .
Postback is basically a property that we can use while doing some tasks that need us to manage the state of the page, that is either we have fired some event for e.g. a button click or if we have refreshed our page.
When our page loads for the very first time , that is if we have refreshed our page, at that time postback-property is false, and after that it becomes true.
if(!ispostback)
{
// do some task here
}
else
{
//do another task here
}
http://happycodng.blogspot.in/2013/09/concept-of-postback-in.html