Is there an inline way to conditionally add an attribute in Ruby?

Question

There are a number of times in Rails when I would like to be able to add an attribute to something only if the attribute is of a particular value.

Let me give you an example. Let's say I want to disable a button based on a particular property such as check_if_user_can_be_added:

link_to 'Create account', new_user_path, disabled: (user_can_be_added?)

This all looks fine and well except that disabled happens to be applied in HTML regardless of what value you give it. If you give a button the attribute disabled: false then it will still be disabled.

What I need

# if the button is disabled
link_to 'Create account', new_user_path, disabled: true

# if the button is not disabled
link_to 'Create account', new_user_path

The way that I can see to do it

Getting this means that you need a solution similar to the following which sets up the options hash first and then passes it in subsequently:

options = user_can_be_added? ? {disabled: true} : {}
link_to 'Create account', new_user_path, options

The way I would like to do it...

This doesn't work but trusting in Ruby's beauty I suspect there's something similar out there. This is basically what I'd like to do

link_to 'Create account', new_user_path, ({disabled: true} if user_can_be_added?)

Can I do it, is there perhaps something using the splat operator that gets me there...?

Answer 1

You can just set nil to cause Rails to ignore the attribute:

link_to 'Create account', new_user_path, disabled: (user_can_be_added? ? true : nil)

For this particular case, you can also use || like so:

link_to 'Create account', new_user_path, disabled: (user_can_be_added? || nil)