I built a .erb file that has a bunch of variables listed in it.
<body>
<h1>
<%= header %>
</h1>
<p>
<%= intro1 %>
</p>
<p>
<%= content1 %>
</p>
<p>
<%= content2 %>
</p>
<p>
<%= content3 %>
</p>
</body>
Then I have a text file with the variables:
header=This is the header
intro1=This is the text for intro 1
content1=This is the content for content 1
content2=This is the content for content 2
content3=This is the content for content 3
I need to take the variables from the text file and insert them into the .erb template. What is the proper way to do this? I am thinking just a ruby script, rather than an entire rails site. It is only for a small page, but needs to be done multiple times.
Thanks
I think a lot of people have come at this from the "how do I get the values out of where they are stored?" and have ignored the other half of the question: "How do I replace <%= intro1 %> with some Ruby variable I have in memory?
Something like this should work:
require 'erb'
original_contents = File.read(path_to_erb_file)
template = ERB.new(original_contents)
intro1 = "Hello World"
rendered_text = template.result(binding)
the binding thing here means that every local variable can be seen inside by ERB when it's rendered. (Technically, it's not just variables, but methods available in the scope, and some other things).
I would skip the txt file, and instead go with a yml file.
Check this site out for a little more info on how to do it: http://innovativethought.net/2009/01/02/making-configuration-files-with-yaml-revised/
I agree about YML. If you really want (or have) to use a text file, you can do something like that :
class MyClass
def init_variables(text)
text.scan(/(.*)=(.*)\n/).each do |couple|
instance_variable_set("#" + couple[0], couple[1])
end
end
end
my_obj = MyClass.new
my_obj.init_variables("header=foo\ncontent1=bar")
Related
Rails 7 / Ruby 3
I'm currently working on a site that requires code examples to be displayed on a page - I can get these to display utilising the extra % character trick, however, for some of the examples I need to have a variable within them that is resolved (e.g. like the users' own API key etc...).
Consider I have #variable = "Resolved Variable"
<%%= link_to #variable, variable_path %>
Outputs on the page explicitly as
<%= link_to #variable, variable_path %>
But I really need the #variable to resolve and show on the page as:
<%= link_to "Resolved Variable", variable_path %>
I've tried all kinds of escaping the variable, but it seems that <%%= ensures that nothing following it can be resolved.
Any ideas?
Any text you haven't html_encodeed will be displayed as plain text.
My suggestion to you is to create a interpolated string that you could use to generate your intended result. For example:
output_text = "<%= link_to '#{#variable}', variable_path %>"
And, not sure if this is what you're looking for, but you can get a good UI by adding some Javascript library to format you code in the language in intend (in this case Ruby, it seems).
In case that's interesting to you, check the Prism lib, or check how to add it to your project here
I hope this helps.
With kind regards,
Rogerio
<%% in ERB will simply output <%, no more, no less. In particular, it won't attempt to parse the code after <%% as Ruby. However, this doesn't mean that you can't have another <%= ... %> after <%%:
require 'erb'
template = <<-EOD
<%%= link_to <%= #variable.inspect %>, variable_path %>
EOD
#variable = "Resolved Variable"
puts ERB.new(template).result
The inspect method will add quotes around your string and also escape certain characters as needed.
Output:
<%= link_to "Resolved Variable", variable_path %>
Could someone explain why it is preferred when embedding ruby for things like page titles to use
<% provide(:title, 'Help') %>
and then using
<%= yield :title %>
rather than jus using a variable:
<% title = 'Help' %>
<%= title %>
I'm assuming its to do with the fact that you can yield before you have called provide() but if that is the case why is it not possible to call the variable before defining it?
Thanks :)
If you want to simply render a variable in the view, the second method will do.
However, provide and yield offer a various ways to build the rendered content. For, example, you pass instance variable like #posts which you may already assign a variable after a complicated algorithm, which you will not do in a view template.
http://api.rubyonrails.org/classes/ActionView/Helpers/CaptureHelper.html
http://guides.rubyonrails.org/layouts_and_rendering.html#understanding-yield
provide (or content_for) are used to pass some elements from the view to the layout, so if you have layout:
<html>
<head>
<title><%= yield :title %></title>
</head>
<body>
<%= yield %>
</body>
</html>
Than in all the views, you can set the content for title with provide or content for. Local variables cannot do this, as they only live in a given view.
provide stores a block of markup in an identifier for later use. In this case, 'Help' in the symbol :title. The provide is enclosed in <% %> to indicate it is executing this code and not printing out in the view.
yield in this case just spits that block back out. The yield is enclosed in <%= %> to indicate it is being printed out into the view.
Think of it as setting a variable and printing out a variable.
See: http://api.rubyonrails.org/classes/ActionView/Helpers/CaptureHelper.html#method-i-provide for more information. Note that provide is really a wrapper for content_for so that's where the good stuff is in that link.
I'm working on a web application that has a view where data is fetched and parsed from a text file (the textfile is only available at the backend, not to the user). I've written a function that takes in the text file and converts it to an array of strings, it's called txt_to_arr. Then I have another function line_fetcher which just calls txt_to_arr and outputs a random string from the array.
In my view, I call the controller's function as so: <% line_fetcher %>.
I've put both txt_to_arr and line_fetcher into the view controller's helper rb file, and when I run rails s, the random string is not rendered at all. I've also tried <% puts line_fetcher %>
I've checked in Bash that the function does output random strings from the text file, so the function does work correctly. Also, the text file being parsed is in the public folder. Does anyone have an idea why this might be?
Thanks a lot!
Try placing the code in the controller and assigning the output to a variable using
a=`line_fetcher` (note the backtics) as detailed at
http://rubyquicktips.com/post/5862861056/execute-shell-commands
and then <%= a %> in your view.
and place the file in the root of your rails app
Simple erb like <%= line_fetcher %> would work good for simple variables.
But if you want output of any model/database instance then do:
<%= ModelName.first.inspect %>
Note the inspect word.
And in case of using HAML do:
=ModelName.first.inspect
In ERB: The <% %> signify that there is Ruby code here to be interpreted. The <%= %> says interpreted and output the ruby code, ie display/print the result.
So it seems you need to use the extra = sign if you want to output in a standard ERB file.
<%= line_fetcher %>
Use <%= %> to output something in your view, so:
<%= line_fetcher %>
I am working on a style guide which displays the code, as well as the output. It is currently structured so that the code only needs to be described once, and is displayed in both its raw and interpreted versions, like so:
<% code = <<PLACE_THE_EXAMPLE_CODE_BETWEEN_THESE_TWO_LINES_EXACTLY_AS_YOU_WANT_IT_TO_APPEAR
<div>
#{ image_tag 'image.png' }
</div>
PLACE_THE_EXAMPLE_CODE_BETWEEN_THESE_TWO_LINES_EXACTLY_AS_YOU_WANT_IT_TO_APPEAR
%>
<%= raw code %>
<%= content_tag :pre, code, class: "prettyprint linenums" %>
This is great, and fairly easy to maintain. The problem comes in with the rails helpers, like image_tag in the above example. The view example correctly displays an image in a div, and the code example displays the relevant HTML. In this case, the relevant HTML includes an anchor tag - the results of the image_tag method, not the call itself.
I would prefer the code examples to display the helper methods, rather that their results. I am able to make this work by specifying the example code in a file, and either rendering or reading the file. I would prefer to make this work by specifying the code in a variable, as above, but I can't seem to get an ERB delimiter to work inside of a string inside of an erb block. Even the simplest case of <% foo = '<%= bar %>' %> doesn't work at all. I've tried playing with the syntax (<%% %%> and % % for example), using details from the official documentation, without much success.
The only information I could find on the matter is here, using <%= "<" + "%=" %> link_to <%= image.css_tag.humanize %> <%= "%" + ">" %> %>, which does not work in this use case (if at all).
So, is there a way to specify a string that contains a ERB end-delimiter (%>) in an ERB string, or am I stuck using the slightly clunkier file-read method? Thanks!
Edit:
What I would like to end up with is a working version of this:
<%# Idealized code - does not work %>
<% code = <<PLACE_THE_EXAMPLE_CODE_BETWEEN_THESE_TWO_LINES_EXACTLY_AS_YOU_WANT_IT_TO_APPEAR
<div>
<% image_tag 'image.png' %>
</div>
PLACE_THE_EXAMPLE_CODE_BETWEEN_THESE_TWO_LINES_EXACTLY_AS_YOU_WANT_IT_TO_APPEAR
%>
So that <%= raw code %> would (continue to) output:
<div>
<img src="/images/image.png" alt="Image" />
</div>
And <%= content_tag :pre, code, class: "prettyprint linenums" %> would output:
<pre class="prettyprint linenums">
<div>
<% image_tag 'image.png' %>
</div>
</pre>
Instead of what it currently does when using a variable, which is:
<pre class="prettyprint linenums">
<div>
<img src="/images/image.png" alt="Image" />
</div>
</pre>
I want users to be able to copy the code example and paste it into a new view, without having to translate HTML back into the helpers that produce them. I think what I basically need is an alternative ERB delimiter, in the same way that ' and " (or even %q{}) vary for strings. It seems that even though the final ERB delimiter is occurring inside of a string, it is being actually processed as the end of the block. The simplest case of <% foo = '<%= bar %>' %> demonstrates somewhat what I want to accomplish. In a generator, you might use <% foo = '<%%= bar %>' %> (or something similar), to tell it not to process as ERB right then and there. This all works fine when reading from a file, or even in a pure rb file (like a helper), but it makes the most sense to put it in the view, in this case, as it is intended to be easily manipulated by our designers.
If I'm understanding you right, your real problem is that heredocs behave like double quotes as far as interpolation is concerned. So all you need is a quoting mechanism that behaves like single quotes. Ruby has lots of string quoting mechanisms, in particular we have %q{...}:
<% code = %q{
<div>
#{ image_tag 'image.png' }
</div>
} %>
You can use other delimiters if you'd like: %q|...|, %q(...), etc. There's still a change of course but at least you don't have to worry about interpolation problems.
If you really want to use a heredoc, you can specify the heredoc terminator with quotes and the corresponding quoting style will apply to the content:
<% code = <<'PLACE_THE_EXAMPLE_CODE_BETWEEN_THESE_TWO_LINES_EXACTLY_AS_YOU_WANT_IT_TO_APPEAR'
<div>
#{ image_tag 'image.png' }
</div>
PLACE_THE_EXAMPLE_CODE_BETWEEN_THESE_TWO_LINES_EXACTLY_AS_YOU_WANT_IT_TO_APPEAR
%>
The single quotes in <<'PLACE...' specify that single quoting rules (i.e. no interpolation) apply to the heredoc's content.
Of course none of that stuff will work with embedded ERB like this:
<% code = %q{
<div>
<% ... %>
</div>
} %>
because the ERB parser will see the first %> as the closing delimiter for the outer <% code... part. Fear not, I think I have a plan that will work without involving gross hacks or too much work.
Some preliminaries:
Rails uses Erubis for ERB processing.
Erubis allows you to change the delimiters with the :pattern option to its constructor.
Rails uses Tilt and Sprockets to handle the template processing pipeline, these allow you to make the right things happen to pancakes.js.coffee.erb in the right order.
Using the above you can add your own template format that is ERB with a different delimiter and you can have Rails use this new format to handle your "special" sections before the normal ERB processing can make a mess of things.
First you need to hook up Tilt. If you have a look at lib/tilt/erb.rb in your Tilt installation, you'll see the Erubis stuff in Tilt::ErubisTemplate at the bottom. You should be able to subclass Tilt::ErubisTemplate and provide a prepare override that adds, say, a :pattern => '<!--% %-->' option and punts to the superclass. Then register this with Tilt and Sprockets in a Rails initializer with something like this:
Tilt.register(Your::Template::Subclass, 'klerb') # "kl" for "kludge" :)
Rails.application.assets.register_engine('.klerb', Your::Template::Subclass)
Now your application should be able to handle .klerb files with <!--% ... %--> as the template delimiters. And you can also chain your klerb with erb using names like pancakes.html.erb.klerb and the file will go through klerb before the ERB; this means that templates like this (in a file called whatever.html.erb.klerb):
<!--% code = <<PLACE_THE_EXAMPLE_CODE_BETWEEN_THESE_TWO_LINES_EXACTLY_AS_YOU_WANT_IT_TO_APPEAR
<div>
<% image_tag 'image.png' %>
</div>
PLACE_THE_EXAMPLE_CODE_BETWEEN_THESE_TWO_LINES_EXACTLY_AS_YOU_WANT_IT_TO_APPEAR
%-->
<!--%= "code = escape_the_erb_as_needed(%q{#{code}})" %-->
<% do_normal_erb_stuff %>
will do The Right Thing.
You'd need a helper to implement the escape_the_erb_as_needed functionality of course; a little experimentation should help you sort out what needs to be escape and in what way.
All that might look a bit complicated but it is really pretty straight forward. I've added custom template processing steps using Tilt and Sprockets and it turned out to be pretty simple in the end; figuring out which simple things to do took some work but I've already done that work for you:
Tilt::Template subclass, you get this by piggy backing on Tilt::ErubisTemplate.
Register with Tilt by calling Tilt.register.
Register with Sprockets by calling Rails.application.assets.register_engine.
...
Profit.
I am in ruby 1.9.2, rails3.
So My website has some structures,
and I want to put menu in a middle of my webpage.
I am doing something like (within application.html.erb file)
blahblahblah
<div id="menu">
<%= yield :menu %>
<div>
blahblhablah
I have a file menu.html.erb which has menu structure for the site.
What can I do if I want to use a file within ./layout folder to be used to be part of that yield :menu? I was wondering, if I have to use content_for for every controller, and within every functions...
Btw, menu.html.erb will be different for each controller, so thats why I am yielding it.
In conclusion, I just want to include one common shared menu.html.erb pretty much everywhere.
You could do something like this in your views:
<% content_for(:menu) do %>
<%= render :partial => "/layouts/user_menu.html.erb" %>
<% end %>
You could try to combine this with controller.controller_name (not sure this works for Rails3) and load a different menu for each controller automatically.
You might consider watching the railscast on layouts, it's concise and helpful.
Numbers 7 and 8.
http://railscasts.com/episodes?search=layout