Add Install And Require Gems Inline Without Gemfile as a Ruby TIL

README.md

@@ -10,7 +10,7 @@ pairing with smart people at Hashrocket.
 
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ruby/install-and-require-gems-inline-without-gemfile.md

@@ -0,0 +1,74 @@
+# Install And Require Gems Inline Without Gemfile
+
+[Bundler](https://bundler.io/) has an _inline_ feature where you can declare
+gems that should be installed and required for the current file without the use
+of a `Gemfile`. This is useful for creating a single-file Ruby script that can
+define its own dependencies.
+
+Require `"bundler/inline"` and then add a `gemfile` block toward the top of the
+script to specify the source and any gems.
+
+```ruby
+require "bundler/inline"
+
+gemfile do
+  source "https://rubygems.org"
+  gem "httparty"
+end
+```
+
+When the script gets run (e.g. `ruby script.rb`), it will install the gems (if
+they haven't already been installed) and then run the script. You can specify
+version constraints just like you'd do in a `Gemfile`.
+
+Here is a single-file script using this approach that I wrote to interact with
+the Kit API.
+
+```ruby
+#!/usr/bin/env ruby
+require "bundler/inline"
+
+gemfile do
+  source "https://rubygems.org"
+  gem "httparty"
+end
+
+require "json"
+require_relative "kit_client"
+
+API_SECRET = ENV["KIT_API_SECRET"]
+
+def fetch_all_tags(api_secret)
+  client = KitClient.new("https://api.kit.com/v4", api_secret)
+
+  tags = []
+  after_cursor = nil
+
+  loop do
+    params = {per_page: 1000}
+    params[:after] = after_cursor if after_cursor
+
+    response = client.get("/tags", params)
+
+    data = JSON.parse(response.body)
+    tags.concat(data["tags"])
+
+    break unless data["pagination"]["has_next_page"]
+    after_cursor = data["pagination"]["end_cursor"]
+  end
+
+  tags
+end
+
+tags = fetch_all_tags(API_SECRET)
+
+tags.each do |tag|
+  puts tag
+end
+```
+
+Because I've specified the shebang at the top of the file (and assuming I've
+`chmod +x fetch_tags.rb`), I can run this directly as a script with
+`./fetch_tags.rb`.
+
+[source](https://bundler.io/guides/bundler_in_a_single_file_ruby_script.html)