Creating Sinatra Extension That Depends On Another Sinatra Extension - ruby

Question

I'm extracting functionality from a sinatra application into an extension. My extension module (ExtensionBar) depends on the existence of class-level dsl extensions created by another extension module (ExtensionFoo). Because of this, my extension dies when required by my main app.
my_app.rb:
require "extension_foo"
require "extension_bar"
class MyApp < Sinatra::Base
register ExtensionFoo
register ExtensionBar
end
extension_foo.rb:
module ExtensionFoo
def with_foo
yield
end
end
extension_bar.rb:
module ExtensionBar
with_foo do
"bar"
end
end
My question: How can I most robustly and simply write an extension that depends on the registry of another extension? I'd like to avoid metaprogramming as much as possible.

Answer 1

In the example you've given, ExtensionBar doesn't do anything to any app. You also need to register the dependent extension in the extension you wish to use in the app. The instructions on writing modules gives a before block as the example for the LinkBlocker DSL, both of which would make your example more like this:
# extension_foo.rb
require 'sinatra/base'
module Sinatra
module ExtensionFoo
def with_foo
warn "Calling with_foo"
s = yield
warn "s = #{s}"
s
end
end
register ExtensionFoo
end
# extension_bar.rb
require 'sinatra/base'
require_relative 'extension_foo.rb'
module Sinatra
module ExtensionBar
before do
warn "Calling with_foo in before"
with_foo do
"bar"
end
end
end
register ExtensionBar
end
# app.rb
require 'sinatra'
require_relative 'extension_bar.rb'
get "/" do
with_foo do
"blah"
end.inspect
end
When I run this I don't get an error and I do see the warnings in my STDOUT, and the output is "blah".
Calling with_foo in before
Calling with_foo
from /Volumes/RubyProjects/Test/extension_dependency/extension_foo.rb:6:in `with_foo'
s = bar
from /Volumes/RubyProjects/Test/extension_dependency/extension_foo.rb:8:in `with_foo'
Calling with_foo
from /Volumes/RubyProjects/Test/extension_dependency/extension_foo.rb:6:in `with_foo'
s = blah
from /Volumes/RubyProjects/Test/extension_dependency/extension_foo.rb:8:in `with_foo'