Question

I am calling an API from a Rails model and I would like to raise an error if the API returns on non-200 code. Otherwise I want to cache/lazy-load the data. This is my method:

def data
    @data ||= SNL.get_list(name)
    raise StandardError, @data.inspect unless @data.success?
    @data
end

This works but I was wondering if I can accomplish this in one line. I tried using the and operator combined with an unless but couldn’t get it to work.

Update: I have accepted tokland’s answer because I asked for one line and he/she provided two very good solutions. In the end I am actually going to use

def data
  @data ||= SNL.get_list(name)
  @data.success? ? @data : (raise StandardError, @data.inspect)
end

for readability. I just hated having a third line just to return @data, since an exception will rarely be raised. I feel odiszapc’s answer is a the best compromise of brevity and readability. Thanks everyone.

Answer 1

I wouldn’t strain to write a one-liner, but you can use tap if you absolutely must:

def data
  (@data ||= SNL.get_list(name)).tap { |d| d.success? or raise StandardError.new(d.inspect) }
end

Also with short-circuited logic:

def data
  (@data ||= SNL.get_list(name)).success? && @data or
    raise StandardError.new(@data.inspect) }
end