Yield and Render in ERB Without Ruby on Rails

template.md

require 'erb'

class Template
    def render(template_name="base")
        ERB.new(File.read("#{template_name}.erb")).result(binding)
    end
end

result = Template.new.render do
    ERB.new(File.read("index.erb")).result
end

puts result

base.erb

<main>
    <%= render "footer" %>
    <%=yield %>
</main>

index.erb

<h1>Index Page</h1>

footer.erb

<h1>Footer here</h1>