Text Interpolator gem

It is a simple library for interpolation of variables inside the text.

Introduction

In ruby you have few options for variables interpolation:

  • interpolation inside the string:
var1 = 'some value 1'
var2 = 'some value 2'

result = "We have var1: #{var1} and var2: #{var2}."

puts result # We have var1: some value 1 and var2: some value 2.
  • interpolation inside file (with embedded ruby - erb):
# some_template.erb

We have var1: <%= var1 %> and var2:  <%= var2%>.

# test.rb

require 'erb'

var1 = 'some value 1'
var2 = 'some value 2'

template = ERB.new(File.read("some_template.erb"))

result = template.result(binding)

puts result # We have var1: some value 1 and var2: some value 2.

This library can be used for interpolation inside file with string syntax. In order to achieve it library uses one ruby trick:

env = {var1: 'some value 1', var2: 'some value 2'}

template = "We have var1: %{var1} and var2: %{var2}."

result = template % env

puts result # We have var1: some value 1 and var2: some value 2.

Usage

It’s straightforward. Here is example of file interpolation:

# some_template.txt

We have var1: #{var1} and var2:  #{var2}.
We have var3: #{settings.var3} and var4:  #{settings.var4}.

# test.rb

require 'text_interpolator'

env = {
  var1: 'some value 1',
  var2: 'some value 2',

  settings: {
    var3: 'some value 3',
    var4: 'some value 4'
  }
}

template = File.read("some_template.txt")

text_interpolator = TextInterpolator.new

result = text_interpolator.interpolate template, env

puts result # We have var1: some value 1 and var2: some value 2.
            # We have var3: some value 3 and var4: some value 4.

You can also interpolate hash on multiple levels:

hash = {
  host: 'localhost',

  credentials: {
    user: "some_user",
    password: "some_password",

    settings: {
      user: "some_user2"
    }
  },

  postgres: {
    hostname: '#{host}',
    user: '#{credentials.user}',
    password: 'postgres'
  },

  mysql: {
    user: '#{credentials.settings.user}',
  }
}

require 'text_interpolator'

text_interpolator = TextInterpolator.new

result = text_interpolator.interpolate hash

p result

# {:host=>"localhost", 
#  :credentials=>{:user=>"some_user", :password=>"some_password", 
#  :settings=>{:user=>"some_user2"}}, 
#  :postgres=>{:hostname=>"localhost", :user=>"some_user", :password=>"postgres"}, 
#  :mysql=>{:user=>"some_user2"}}