Question

I have a collection of objects. There are 3 properties in each object

‘id’, ‘name’, ‘is_primary’

The collection of objects will usually have anywhere from 1 to 5 objects.

What I want to do is check the collection to see if is_primary is true. If so output the name, or at least return it.

I want to do this in 1 line of code if possible. I am trying to slim up this one line for erb output in rails. Later in the page i’ll output them all. I thought I had it, but if I return nil it adds extra space which shifts all the html oddly.

Thanks.

Answer 1

Hmm, this doesn’t quite work if no element is_primary…I’m still thinking…

c.detect(&:is_primary).name

Ok, how about:

((a = c.detect(&:is_primary)) && a.name).to_s

As it happens, it is OK in an erb template for the <%= expression to return nil, that just results in an empty string, so for that case you can use:

(a = c.detect(&:is_primary)) && a.name

Update: Responding to the first comment, I do have a test case that I didn’t post…

class A; attr_accessor :is_primary, :name, :id; end
t = [A.new, A.new, A.new, (a = A.new; a.name = 'xyz'; a.is_primary = true; a)]

puts (a = t.detect(&:is_primary)) && a.name

puts ((a = [].detect(&:is_primary)) && a.name).to_s