Rails 5 - in link_to, how to pass a nil (NULL) param?

Question

I have a link where I need to pass a sequence of params, where 2 params are always nill.

link_to go_to_action_path(id, par_01, par_02, par_03, par_04)

In some cases are the par_01 and par_02 nil, in other par_03 and par_04.

If I have these values in the variables:

par_01 = nil
par_02 = nil
par_03 = 'a'
par_04 = 'b'

And then in the go_to_action action:

p01 = params[:par_01]
p02 = params[:par_02]
p03 = params[:par_03]
p04 = params[:par_04]

I get these values:

p01 => a
p02 => b
p03 => 
p04 =>

In other words, the variables par_01 and par_02 will be thrown away and on their places will be moved in par_03 and par_04.

How can I force the link_to to accept a param with a nil value? I was thinking about placing there 0s instead of nils and then manually parse it in the controller action, but this is quite an ugly solution.

Not sure we have enough to go on. What is `go_to_action_path`? Is it a route? If so, what? If a method, we need the source. — Philip Hallstrom, May 20 '18 at 15:29
That's an example of a path to a controller action (yes, it is a route). The above is a pseudocode. The question here is how to pass a `nil` value through a param and "receive" it on the other end in the controller action. — user984621, May 20 '18 at 15:32
Nimish's answer is probably the right one, but it would really help to see that controller action. Otherwise we can only guess. — Philip Hallstrom, May 20 '18 at 15:43
Have you tried using `&` in your ERB? Simply put, it lets code work even if a param is `nil`. — Jake, Jan 18 '19 at 23:49

score 3 · Answer 1 · answered May 20 '18 at 15:40

You can pass hash as the second option with id in your route

Use

link_to go_to_action_path(id, { par_01: par_01, par_02: par_02, par_03: par_03, par_04: par_04 })

Instead of

link_to go_to_action_path(id, par_01, par_02, par_03, par_04)

Then, In Controllers, say action name is action

# here you can use your params
def action
  p01 = params[:par_01]
  p02 = params[:par_02]
  p03 = params[:par_03]
  p04 = params[:par_04]
end

Rails 5 - in link_to, how to pass a nil (NULL) param?

1 Answers1