calling a controller action with argument from rack middleware

Question

Is there a way I could pass an argument to a controller action call from middleware? This is the action in controller code ``` # in my_controller.rb # def print_name(name) render :text => "Hello, #{name}!" end ``` Here's the code from my middleware that calls this action ``` # in middleware # def call(env) env['action_controller.instance'].class.action(:print_name).call(env) end ``` This of course raises `ArgumentError`. I'm unaware how can I pass an argument to `action` call. Here's the source: ``` # in action_pack/lib/action_controller/metal.rb # def self.action(name, klass = ActionDispatch::Request) middleware_stack.build(name.to_s) do |env| new.dispatch(name, klass.new(env)) end end ``` As you can see, it returns a rack endpoint from provided controller action. I see no way I could pass an argument here. I ended up changing the controller dynamically with `class_eval` and then calling the controller method from that proxy method. ``` # in middleware # def define_proxy_method(klass…

Accepted Answer

You don't want to put arguments on your action. Middleware should only interact with the request environment, not try to call into the controller directly.

You can pass the same value in the params hash:

```
# middleware
#
def call(env)
  request = Rack::Request.new(env)
  request['name'] = get_name
end
```

and read from the params hash in the controller:

```
# my_controller.rb
# 
def print_name
    render :text => "Hello, #{params['name']}!"
end
```

calling a controller action with argument from rack middleware

Solution

Problem