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@stevenharman
Last active December 16, 2020 17:28
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Render Ruby ERB templates, inline, with variables bound and available local variables in the template. ✨ This technique is useful for rendering test fixtures via ERB, for example.
require "ostruct"
# A wrapper around a single ERB template that will bind the given Hash of values,
# making them available as local variables w/in the template.
class ErbNow < OpenStruct
# Render a given ERB +template+ string, binding the entries in the given +attrs+ Hash
# as local variables in the template, with the key as the variable name.
#
# @example
#
# template = <<~ERB
# <h1>Hello, <%= name %>!</h1>
# <p>The current time is: <time datetime="<%= timestamp %>"><%= timestamp.strftime("%d of %B, %Y")%></time>.</p>
# ERB
#
# ErbNow.render(template, name: "Alice", timestamp: Time.now)
#
# => <h1>Hello, Alice</h1>
# => <p>The current time is: <time datetime="2020-12-16 10:31:36 -0500">16 of December, 2020</time>.</p>
#
# @param [String] template An ERB template, as a String.
# @param [Hash] attrs A Hash of values to be bound to the template, with the key as the local name.
def self.render(template, attrs = {})
new(attrs).render(template)
end
def render(template)
ERB.new(template).result(binding)
end
end
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stevenharman commented Dec 16, 2020

This could be made more robust by accepting an IO-object, or a String-ish object as the template param. Something like

def render(template)
  template = template.read if template.respond_to?(:read)
  template = String(template)
  ERB.new(template).result(binding)
end

To date I've not needed this extra machinery, but please let me know if you do! I'm curious to know how others might use this technique.

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