Question

I find that I’m often doing things of this sort in my Ruby code:

if person
  if person.shirt
    if person.shirt.sleeve
    ...
  end
end

..which I do to avoid NoMethodErrors. I’m wondering if there’s any way that I can collapse this into one line, without the obvious

if person && person.shirt && person.shirt.sleeve

Basically, I want to make my code more compact.

Answer 1

Inside those ifs you want to do something with a sleeve, right?

Rails has a nice helper, try. It returns value if everything goes well, and nil otherwise. So, in this example, if person.shirt or even person itself is nil, try will return nil as well.

if sleeve = person.try(:shirt).try(:sleeve)
  # do your stuff
end

For vanilla ruby you can use andand gem which provides similar functionality.

if sleeve = person.andand.shirt.andand.sleeve
  # do your stuff
end

Since ruby 2.3, you can use safe navigation operator:

if sleeve = person&.shirt&.sleeve
  # do your stuff
end