I can't believe I haven't found other questions to answer this but I've searched high and low and can't find anything that really answers my question.
Basically, I have an Expenses page in which I want to display all Expenses in a given month in a table. I have a month and year select and right now I have it working by adding month and year parameters to the url and going to that href with a little javascript. I would like to avoid a page refresh however and just update the table when the select box value is changed. As I understand it, because I'm not using a form, I can't use :remote => true and thus have to use AJAX. My research has brought me to set things up as the following.
This is my JQuery with an AJAX call:
$(document).ready(function() {
$('#monthSelect').change(function() {
// alert("yay");
var m = $(this).val();
var y = $("#yearSelect").val();
$.ajax({
type: "GET",
url: "/expenses",
data: { month : m, year : y } ,
success: function(data) {
},
dataType: "json"
});
});
});
#monthSelect and #yearSelect are the ids of my two select boxes. This part seems to work. When I change the value of the month select box, it sends the GET request to "/expenses" with the correct month and year in the params.
/expenses naturally routes to my index action. Here is the part where I'm confused.
def index
#expenses = # Code that gets the expenses that correspond to the month and year in the params.
# This part works. I've tested it and #expenses are all the records I want
respond_to do |format|
format.html
format.json { render json: #expenses, status: :ok } #?????
end
end
So I guess my primary question is how the json part works, and if I should even be using json in the AJAX. Tutorials and videos I've looked at all seem to imply that getting the response in json is the way you're supposed to do it, but I'm not sure what "rendering json" even means. My understanding is that passing #expenses, it basically will render what #expenses.to_json returns, which is just a bunch of json, key-value pairs. How do I take that and make a table?
A friend of mine that has done plenty of AJAX but no Ruby on Rails said that I can just write the HTML in the AJAX success function
...
success: function(data) {
$("#expenses-table").html("HTML of my Table");
}
But this just doesn't seem like the Rails way, to put a bunch of Javascript code that just puts HTML into a string. And then what does the render: json do if I'm just putting the HTML in the AJAX? I did see an answer here on Stack Overflow that had
success: function(data) {
$("#expenses-table").html(data);
}
which would be nice, since data does have all the json I want. But obviously that doesn't just work like that.
So if I could get some clarification on this whole mess, if I'm even approaching it right with JSON, or if I should just write the HTML in the AJAX, that would be much appreciated.
EDIT 1:
Here's my current table code:
<table id="expenses">
<thead>
<tr>
<th>Description</th>
<th>Amount</th>
<th>User</th>
<th>Date</th>
<th colspan="3"></th>
</tr>
</thead>
<tbody>
<% #expenses.each do |expense| %>
<tr id="expenses-row">
<td><%= expense.description %></td>
<td><%= number_to_currency expense.amount %></td>
<td><%= expense.user.name %></td>
<td><%= expense.date.strftime("%m/%Y") %></td>
<td><%= link_to 'Show', expense %></td>
<% if expense.user == #user %>
<td><%= link_to 'Edit', edit_expense_path(expense) %></td>
<td><%= link_to 'Delete', expense, method: :delete, data: { confirm: 'Are you sure?' } %></td>
<% else %>
<td></td>
<td></td>
<% end %>
</tr>
<% end %>
</tbody>
</table>
Basically just the standard scaffold table. Most of the changes were just css. Here's what the json looks like for one record
[{"id":8,"description":"This is a test","amount":"35.0","user_id":1,"date":"2014-10-01","created_at":"2014-10-03T07:07:53.412Z","updated_at":"2014-10-03T07:07:53.412Z","receipt_file_name":null,"receipt_content_type":null,"receipt_file_size":null,"receipt_updated_at":null}]
I guess I'd rather do the code in ERB/ruby as I'm more immediately familiar with it. Though it almost feels a little pointless to have the json since #expenses is what I already use in my current table code. However, wouldn't render :file "expenses_table.html.erb" refresh the whole page? Or how would it know where to render just that table and replace what was previously there? It almost sounds easier to respond to format.js and make an index.js.erb because I know I could replace the html with my partial. But I haven't tried that as all the examples I've seen respond to format.json. If it sounds like I'm just confused and don't know what's going on it's because I am. I just need some clarification. Thanks for your help!
if I should even be using json in the AJAX.
You can use any type of String you want. The problem is parsing the string on the javascript side to extract each piece of data. For instance, you could respond with a String such as:
"exp1=10, exp2=20, exp3=30"
Then your javascript code can split the String on ", ", then the "=" sign, then use the pieces to create an object, then you can use the object to refer to the data. On the other hand, if the data is sent as a JSON string, all you have to do in the javascript is:
var obj = JSON.parse(data);
...and obj will be something similar to a ruby Hash, where you can look up keys to get values.
So I guess my primary question is how the json part works...My
understanding is that passing #expenses, it basically will render what
#expenses.to_json returns, which is just a bunch of json, key-value
pairs. How do I take that and make a table?
That's correct. You make the table using your programming skills.
A friend of mine that has done plenty of AJAX but no Ruby on Rails
said that I can just write the HTML in the AJAX success function
Sure, but the trick is still to programmatically take the data in the json and insert it into an html table. If you want to go that route, you could return a complete table as the response, so that you can use ERB/Nokogiri/ruby on the server side to insert the data in the table. Then you would write something like:
#expenses = ....
render :file "/some/dir/expenses_table.html.erb"
Another approach might be to give each <td> in the table an id attribute that is equal to a key in your json data. Then you can use javascript to loop over each key in the json data, look up the <td> with that id, then replace the entry with the value in the json data corresponding to the key.
If you want more concrete suggestions, you'll have to post a small example of your table's html as well as what #expenses.to_json looks like.
By the way, the jQuery ajax() function has too many features, so all of the common ajax requests have shortcut functions, where the relevant options are filled in for you, e.g. getJSON(), where you just specify the url, data, and the success function. In this case, that doesn't save you much work, but maybe the function name is more descriptive than 'ajax'.
Response to comment questions:
I guess my confusion then is which javascript is this? Is this the
original AJAX call?
Yes. That is the only javascript you need to code.
Should that be in a js.erb file then for me to
call some ruby code?
No. You would use a js.erb file if you want to create some js using ruby (that is what erb is for), AND you want to return js code as the response. We've established that you don't want to return javascript as the response. However, using rails to setup ajax is very confusing, so I may not be understanding the gist of your questions. It's much simpler not to use rails to generate ajax javascript.
As far as I understand things, if you put remote: true in your rails html helper when you create an html form, then when the form is submitted, a request is sent to your rails app with an Accept header of text/javascript. That means if your action has a respond_to block with a format.js line, that line will execute, and you can send some javascript back to the browser, e.g. a .js.erb file that contains code that performs an ajax request to get your expense data. Your browser will immediately execute the returned js, which will send an ajax request back to the server asking for the expense data. Note that the rails way is inefficient: the browser has to send two requests to the server to accomplish one ajax request: one request is sent to the server to get the js code that will make an ajax request for the expense data, then the browser executes the ajax code which sends another request to the server to get the expense data.
Or can I call a javascript file in the respond
to?
It looks to me like you want to replace the existing table with a whole new table, i.e. you are not changing two or three <td>'s in the existing table, which should makes things very easy. In fact, as far as I can tell, you can use the same erb code that you used to create the existing table to create the new table. However, your index action's response to an ajax request should only return the table--not the whole page. That suggests you should put the code that creates the table into a separate template, a partial:
views/shared/_table.html.erb:
<table id="expenses">
<thead><th>Description</th><th>Amount</th><th>Date</th></thead>
<% #expenses.each do |expense| %>
<tr>
<!-- I used an abbreviated Expense model: -->
<td><%= expense.description %></td>
<td><%= number_to_currency expense.amount %></td>
<td><%= expense.date %></td>
</tr>
<% end %>
</table>
Then you include the partial in views/expenses/index.html.erb:
<h1>Expenses#index</h1>
<p>Find me in app/views/expenses/index.html.erb</p>
<div>
<select id='expense_day'>
<option value="all">All</option>
<option value="2014-10-5">10/5/14</option>
<option value="2014-10-6">10/6/14</option>
</select>
</div>
<%= render "shared/table" %> <!-- HERE -->
By default, render() will look for a partial in the app/views directory called shared/_table.html.erb.
Those two files combined (inserted into the application layout) make up the index.html.erb view. Because the table is now a separate template, just the table can be rendered in response to an ajax request:
class ExpensesController < ApplicationController
def index
respond_to do |format|
if request.xhr? #Is this an ajax request?
target_date_str = params['target_date']
if target_date_str == "all"
#expenses = Expense.all
else
#expenses = Expense.where(date: Date.strptime(target_date_str, "%Y-%m-%d"))
end
#Render just the table for the ajax request:
format.html { render partial: "shared/table" }
else #then not an ajax request
#expenses = Expense.all
format.html #By default renders index.html.erb
end
end
end
end
respond_to() looks at the Accept header in the request and based on that chooses a matching format:
format.html
format.json
format.xml
etc.
I examined the request sent by jQuery's .get() ajax function, and it sends a request with an Accept header of text/html as the highest priority, so format.html will be chosen in the respond_to block. Edit: I originally wrote the index action thinking there would be a format.json line for the ajax request, and a format.html line for a non ajax request. But because the index action now returns html in both cases, the respond_to() block isn't needed:
class ExpensesController < ApplicationController
def index
if request.xhr? #if an ajax request...
target_date_str = params['target_date']
if target_date_str == "all"
#expenses = Expense.all
else
#expenses = Expense.where(date: Date.strptime(target_date_str, "%Y-%m-%d"))
end
render partial: "shared/table" #Overrides rails default operation which renders index.html.erb
else #then not an ajax request
#expenses = Expense.all #rails defaults to rendering index.html.erb
end
end
Here is the javascript I used:
<script>
$( document ).ready(function() {
$("#expense_day").on("change", function() {
var selected_date = $(this).val();
$.get(
"/expenses",
{ target_date: selected_date },
function(table) {
$("#expenses").replaceWith(table)
}
);
});
});
</script>
<h1>Expenses#index</h1>
<p>Find me in app/views/expenses/index.html.erb</p>
<div>
<select id='expense_day'>
<option value="all">All</option>
<option value="2014-10-5">10/5/14</option>
<option value="2014-10-6">10/6/14</option>
</select>
</div>
<%= render partial: "shared/table", expenses: #expenses %>
I put the javascript in the index.html.erb view, which should make it clear that the javascript is part of the html page. However, you can remove the javascript from index.html.erb and put it in another file--but eventually the js has to find its way back into the index.html.erb file. Here are some links that discuss alternate locations for the javascript:
Why is rails not rendering the .js.erb file?
Best way to add page specific javascript in a Rails 3 app?
Rails has something called the asset pipeline, which is a method for cramming all the javascript and css into as few lines as possible by removing all the whitespace. Because the files are smaller, your browser can load them faster. To take advantage of that minifying, you have to put your assets, i.e. your javascript and css files, into certain directories. That is really not something you need to worry about because your javascript code is not thousands of pages long.
I've been looking into how to use a javascript variable within erb <% %> tags. This will have to be done via AJAX (see How to pass a javascript variable into a erb code in a js view?). I'm quite new to JS and especially new to AJAX and finding an example of this in action would be awesome.
Consider the following simple scenario where all that is needed to be passed from the JS to the ERB is a simple bit of text:
HTML:
<input id="example-input" type="text">
$(function() {
$('input#example-input').keyup(function(e) {
if(e.keyCode == 13){
var input = $('input#example-input').val();
<% puts input.upcase %>
}
}
});
Notice that the input will not be defined within the erb tags, and hence this will throw an error.
I believe you're assuming that the line <% puts input.upcase %> will execute ruby code after your javascript line var input = $('input#example-input').val();. If that is what you were thinking, this is incorrect. In the example you've given:
The <% puts input.upcase %> gets executed when the page loads.
input in <% puts input.upcase %> is a ruby variable
input in var input = $('input#example-input').val(); is a javascript variable
If you had a variable that you set on the server side, you could say something like this in your javascript:
var my_js_var = '<%= a_str_in_ruby %>';
and that would work fine for intializing a variable on the javascript side.
However since you want to request data from the client side (aka javascript) to your server side (to be handled by rails controller), what you should be doing is submitting an ajax request. There's a section in the rails documentation that contains examples, and a good railscasts episode (if you're a paying member).
I'm using Ruby on Rails.
Here is my code for the view, where I make a post to the controller, passing parameter "tplangroup.id":
<div id="collapse">
<%= form_tag(tplans_collapse_tplans_path, :method => 'post', :remote => true ) do %>
<%= hidden_field_tag(:tplangroup_id, tplangroup.id) %>
<% end %>
</div>
Here is my code on the controller end, where it parses the necessary data and shoots back array "#ordered_tplans"
def collapse_tplans
#collapsed_tplangroup = Tplangroup.find(params[:tplangroup_id])
tplans_from_tplangroup = #collapsed_tplangroup.tplans
#ordered_tplans = tplans_from_tplangroup.order("favrank DESC")
return #ordered_tplans
end
Since I called :remote => true in the original form located in the view, it passes this array to a file called "collapse_tplans.js"
My question is: what is the best way/practice to parse through this array now passed to the js file, and display its contents in the view? Do I use rails code in the js file to manipulate the object? Or do I do it all in javascript/jquery? What is the best practice, and could you provide any example?
Thanks!
Really kind of depends on how you want to go about it, as with all code, there are many ways to skin a cat. I find the easiest way is to use the return ujs as an erb file (collapse_tplans.js.erb) and from there, choose the element on the page you want to attach the retuned object to, and call a standard erb or haml partial where your iterations can be done clearly.
e.g.
In collapse_tplans.js.erb
$('#my_wacky_element').append("<%= j render(:partial => 'collapse_tplans', :locals => { :ordered_tplans => #ordered_tplans }) %>");
Then in
_collapse_tplans.html.erb
<ul>
<%= ordered_tplans.each do |tplan| %>
<li><%= tplan.attribute %></li>
Here is a RailsCast on how to pass data to js from rails:
http://railscasts.com/episodes/324-passing-data-to-javascript?view=asciicast
How can I loop server side code on the client without javascript? I have this loop in my rails app
//partial = _manufacturers
<div id="all_manufcaturers">
<% for manufacturers in #manufacturerss%>
ID: <%= h manufacturers.id %>
<% end %>
</div>
How can I render this using ajax? I know something like the following works since it is just a static replacement:
$("#manufacturers_count").html('Manufacturer - <%= #car.manufacturers.count %>');
But pseudocode like this does not work since the partial contains a loop:
$("#all_manufacturers").html('...render(manufacturers)...');
Yes, it can be done. You will want to make a server side script (e.g php) that builds a dataset for you and echos it with json_encode. You will then want to parse the response from the request with the appropriate javascript decode function in whatever library you're using (example, jQuery.decodeJSON()). You can then loop through the response set and render.
I am doing Ajax Call from View, then controller is fetching data from DB into an Array, now this array value I want to pass to JavaScript, so that I can update data in a table with different id's
Controller code:
def AjaxView
#var1 = Var.find(:all,:conditions => { :varname=> "one" },:select=> (params[:col]))
respond_to do |format|
format.js
end
end
AjaxView.js.erb code:
$(document).ready(function() {
$("#test").text("valuetoupdate");
});
Now when I run this code it successfully update "valuetoupdate" at id =test in view page.
Instead of this I want to update all values one by one from array #var1.
I searched more and realized that array #var1 generated in Controller will automatically get transferred to AjaxView.js.erb file. Now I have to iterate over all values, but this code doesn't work in JavaScript file:
<% for var in #var1 %>
$("#3").text(var);
<% end %>
it gives blank response
Thanks Guys,
I am able to resolve my issue, in following manner,
I moved away from for loop implementation, instead start using if else condition,
<% if #var.to_s == 'valuetoupdate' %>
{ }
<% elsif #var.to_s == 'valuetoupdate1' %>
{}
And it worked fine for me.