Ruby templates: How to pass variables into inlined ERB?

Question

Hello!

I have an ERB template inlined into Ruby code:

require 'erb'

DATA = {
 :a => "HELLO",
 :b => "WORLD",
}

template = ERB.new <<-EOF
 current key is: <%= current %>
 current value is: <%= DATA[current] %>
EOF

DATA.keys.each do |current|
 result = template.result
 outputFile = File.new(current.to_s,File::CREAT|File::TRUNC|File::RDWR)
 outputFile.write(result)
 outputFile.close
end

I can't pass the variable "current" into the template.

The error is:

(erb):1: undefined local variable or method `current' for main:Object (NameError)

How do I fix this?

Answer 1

I can't give you a very good answer as to why this is happening because I'm not 100% sure how ERB works, but just looking at the ERB RDocs, it says that you need a binding which is a Binding or Proc object which is used to set the context of code evaluation. Trying your above code again and just replacing result = template.result with result = template.result(binding) made it work.

I'm sure/hope someone will jump in here and provide a more detailed explanation of what's going on. Cheers.

EDIT: For some more information on Binding and making all of this a little clearer (at least for me), check out the Binding RDoc.

Answer 2

EDIT: This is a dirty workaround. Please see my other answer.

It's totally strange, but adding

current = ""

before the "for-each" loop fixes the problem.

God bless scripting languages and their "language features"...

Answer 3

Got it!

I create a bindings class

class BindMe
 def initialize(key,val)
  @key=key
  @val=val
 end
 def get_binding
  return binding()
 end
end

and pass an instance to ERB

dataHash.keys.each do |current|
 key = current.to_s
 val = dataHash[key]

 # here, I pass the bindings instance to ERB
 bindMe = BindMe.new(key,val)

 result = template.result(bindMe.get_binding)

 # unnecessary code goes here
end

The .erb template file looks like this:

Key: <%= @key %>