CODEWITHSUNDEEP
rubyruby-on-rails-4
Jenny Blunt
Jenny Blunt

Reputation: 1596

In Rails, why are my controller params being modified by the class

I have a controller action somewhat similar to this:

def reports
  puts params
  @stats = Client.stats(params)
  puts params
end

The initial params might look like this:

{ end: '2012-01-01 21:00:19' }

And in my Client model, I have this:

def self.stats(opts)
  opts[:start] = (Time.now - 30.days).to_i
  ...do some calculations..
  return stats
end

If I inspect the params object that was sent before and after the function runs, I can see it's been modified by the self.stats method.

In the example above, I'm not sending 'start' in the initial params, the method adds it for the calculations - as expected.

What I was not expecting was that the function would modify the original hash!

Can someone explain why this is happening?

--EDIT--

I forgot to say I tried to create a copy of the params and use that instead, same issue.

def reports
  a = params
  @stats = Client.stats(a)
  puts params
end

The params are still updated?!

Upvotes: 1

Views: 149

Answers (2)

guitarman
guitarman

Reputation: 3310

That's, because your function call gets a reference to the params not a copy. If you do something like opts[:start] = (Time.now - 30.days).to_i you are editing the params object.

a = params: now both variables point to the same place in the memory. You copied the pointer only.

Google for ruby object copy or ruby deep copy or search at stackoverflow for it. At a first try you could try params.clone.

Upvotes: 4

Veeru
Veeru

Reputation: 356

Whenever you are updating any value of params, take a copy of params like this

a = params.clone

It will create a new element in memory

if you do like this it wont create a new element in memory it will point the same memory

a = params

Try this

Upvotes: 1

Related Questions