Is there a way to list the available variables in an Ruby ERB template?

Question

Hi All,

Suppose I have a Ruby ERB template named my_template.html.erb, and it contains the following:

<div><%= @div_1 %></div>
<div><%= @div_2 %></div>
<div><%= @div_3 %></div>

Is there a way I can programatically list out all the available variables in the template?

For example, the following method:

def list_out_variables
  template = File.open("path_to/my_template.html.erb", "rb").read
  erb = ERB.new( template )
  erb.this_method_would_list_out_variables  
end

would return something like:

['div1','div2','div3']

Any help would be greatly appreciated.

Thanks, Mike

Answer 1

To get a list of variables available to your .erb file (from the controller):

Add a breakpoint in the erb:

<% debugger %>

Then type instance_variables in the debugger to see all of the available instance variables.

Added: Note that instance_variables is a method available from the Ruby class Object and all of its subclasses. (As noted by @mikezter.) So you could call the method programmatically from within your sw rather than using the debugger if you really wanted to.

You'll get back a list of instance variables for the current object.

Added: To get a list of the variables used by an .erb file:

# <template> is loaded with the entire contents of the .erb file as
# one long string
var_array = template.scan(/(\@[a-z]+[0-9a-z]*)/i).uniq