accessing deeply nested params rails

Question

I am writing a piece of code in my controller that is suposed to take the data a user inputs in the form of 00:00 and convert that into minutes before sending it to the model. The code I am using is pretty simple, just split the :duration parameter at the colon and multiply hours by 60 and add the minutes to that number. When I submit the for I get an error when it tries to perform split on a nil object. This must mean I am not accessing the parameter correctly but I am confused as to how I would navigate to a deeply nested parameter and cant seem to find any documentation regarding deeply nested parameters.

Here is my model organization:

log_entry >>
has many
workouts >>
has many 
workout_times, which has :duration as an attribute

This is the code within my log_entries_controller:

def convert_duration
  hours, minutes = params[:log_entry][:workout][:workout_time][:duration].split(":")
  params[:log_entry][:workout][:workout_time][:duration] = (hours.to_i * 60 + minutes.to_i)
end

I have tried all the ways I could think of to write the params part but I cants seem to get it right. I am pretty new to rails/programming so there might be somthing totally obvious I am missing...

EDIT

Here is the log info of parameters past:

Parameters: {
  "commit" => "Save",
  "log_entry" => {
    "date(1i)" => "2011",
    "date(2i)" => "10",
    "date(3i)" => "13",
    "workouts_attributes" => {
      "0" => {
        "time_of_day" => "AM",
        "summary" => "",
        "workout_times_attributes" => {
          "0" => {
            "duration" => "2:00",
            "zone" => "1",
            "_destroy" => "false"
          }
        }
      }
    }
  },
  "authenticity_token"=>"zD6qS6jOSQ3/mRyH7RAgAzWYmwHub0+uBG1sjPVvkEY=",
  "utf8"=>"\342\234\223"
}

Added info to post, it looks like the structure I was expecting..? — Graeme
– Graeme, Commented Oct 14, 2011 at 0:56

Koby · Accepted Answer · 2011-10-14 17:43:04Z

1

You could just assign the parameter you want to your model like so:

def save
  workout = Workout.new(params[:workout])
  workout.workout_time.duration = convert_duration(workout)  
end

Then in your convert_duration method do:

def convert_duration(workout)
  hours, minutes = workout.workout_time.duration.split(":")
  (hours.to_i * 60 + minutes.to_i)
end

In Ruby the last statement of a method is returned, so this would return your calculated duration back to the save method which will set the duration on the workout_time object for the workout object we created from the parameters passed to the method.

edited Oct 14, 2011 at 17:43

answered Oct 14, 2011 at 2:27

Koby

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9 Comments

Graeme Over a year ago

Do you mean put that in the controller? I tried replacing my convert_duration function with this but it didn't seem to effect what was stored in database at all:

def convert_duration       workout = Workout.new(params[:workout])       workout.workout_times.each do |time|       hours, minutes = time.split(":")       time = (hours.to_i * 60 + minutes.to_i)     end

Graeme Over a year ago

The reason I am doing this in the controller is when I try to adjust the :duration in the model it seems to have already converted the hours to an integer and dropped the rest, causing 03:23 to turn into 3. This is why I am trying to do the logic in the controller before the model gets to it.

Koby Over a year ago

I've modified my answer so that it might be more clear. You basically assign the params to a new Workout object, and you can pass that object to the convert_duration method, which gives you access to the items you need.

Graeme Over a year ago

I added those mothods and initially it was throwing an error of no workout_time method for workout, I corrected it by rewriting it to accept multiple workout_times, passing each duration to the convert_duration() function. This still doesnt seem to work though and I actually dont really understand how creating a new Workout object would effect the outcome since the model is looking for the Log_Entry object passed by the create method containing the deeply nested attributes. Can't I can simply access the duration parameters before they are passed to the model using my before_filter?

Koby Over a year ago

your params are the data for your objects, that's why doing something like Log_Entry.new(params[:log_entry] works if the parameters your passing match those of the object. If you're Log_Entry, Workout and Workout_Time models don't match what you're passing via your params, you're only complicating your life. Assigning the params to an object allows you to access the data via the model rather than doing the long list of params like you have in your example in your original post. It's much easier to do workout.workout_time.duration than params[:log_entry][:workout][:workout_time][:duration]

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