Ruby templates: How to pass variables into inlined ERB?

Question

I have an ERB template inlined into Ruby code:

require \'erb\'

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

template = ERB.new <<-EOF
          


        

Answer 1

As others said, to evaluate ERB with some set of variables, you need a proper binding. There are some solutions with defining classes and methods but I think simplest and giving most control and safest is to generate a clean binding and use it to parse the ERB. Here's my take on it (ruby 2.2.x):

module B
  def self.clean_binding
    binding
  end

  def self.binding_from_hash(**vars)
    b = self.clean_binding
    vars.each do |k, v|
      b.local_variable_set k.to_sym, v
    end
    return b
  end
end
my_nice_binding = B.binding_from_hash(a: 5, **other_opts)
result = ERB.new(template).result(my_nice_binding)

I think with eval and without ** same can be made working with older ruby than 2.1

Answer 2

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 %>

Answer 3

In the code from original question, just replace

result = template.result

with

result = template.result(binding)

That will use the each block's context rather than the top-level context.

(Just extracted the comment by @sciurus as answer because it's the shortest and most correct one.)

Answer 4

This article explains this nicely.

http://www.garethrees.co.uk/2014/01/12/create-a-template-rendering-class-with-erb/