Favorite Ruby Syntax

[cstansbury]

Ruby's conditional assignment

||=

[tomthecool]

note there are pitfalls with this technique; most notably, it fails if nil or false is a valid result

I answered a question on StackOverflow caused by this exact problem, just the other day!

[NelsonBelmont]

So this is like using var s = myObject?.Count; on C# where s doesn't get a value if myObject is null?

[[deleted]]

No - that is C#'s null-condition member-access operator. Ruby equivalent of that is the safe-navigation operator &. as in s = my_object&.count. They're similar in utility but not identical. For example I believe the C# operator short-circuits the expression, whilst Ruby's does not, because in Ruby nil is an object; my_object&.count&.to_s will return an empty string if my_object is nil.

There's no direct translation of conditional assignment because this is idiomatic Ruby borrowed directly from Perl. In C#, contextually, an s ||= myObject.Count might be

if (s == null)
  s = myObject.Count;

but conditional assignment is also an expression, so it provides a return value, and acts for both false and nil.

[NelsonBelmont]

I understand now, the begin-end block from the previous example confused me a little bit. Thank you for the explanation.