Ruby on Rails: How do detect if access by JSON?

Question

I got a GET URL that calls a controller method getInfo. It can be called by mydomain.com/getInfo.json?params=BLAHBLAH or mydomain.com/getInfo?params=BLAHBLAH

In the cont

Answer 1

Here is an actual somewhat contrived working example, that answers the question of how to detect if the call is JSON / XML API call vs an "HTML" call. (Accepted answer doesn't answer that question, just tells you how to respond to various formats)

# We can use this in a before_filter
skip_before_action :verify_authenticity_token, if: :api_request?

# Or in the action
def show
  @user = if api_request?
            User.where(api_token: params[:token]).first
          else
            User.find(params[:id])
          end
  respond_to do |format|
    format.html 
    format.json { render :json => @user }
  end
end

private
  def api_request?
    request.format.json? || request.format.xml?
  end

Using a respond_to sets different types of responses, but it doesn't tell your application how the call was made unless you add some extra code that does it (see below for a crude example, just to illustrate the point.)

I wouldn't recommend this, interrogating request is much safer, and 10x times more useful, as the approach below is only useful much later in the request lifecycle ( right before the response is sent back to the client). If you have any logic in your before filters this wouldn't work at all.

# Have no way of using it in a before_filter
# In your controller
def show
  # I want to know if the call was JSON API - right here 
  # This approach wouldn't help at all. 
  @user = User.find(params[:id])
  respond_to do |format|
    format.html { @api_request = false}
    format.json { @api_request = true; render :json => @user }
  end
end

def api_request?
  @api_request
end