This may be a well-know Ruby trick, but I thought I’d share it anyway.
Ruby has the ternary operator:
a = true ? 'a' : 'b' #=> "a" b = false ? 'a' : 'b' #=> "b"
But it also has something else…
a = (true && 'a') || b #=> "a" b = (false && 'a') || b #=> "b"
All statements in Ruby return the value of the last expression evaluated, so
true && 'a' returns ‘a’, and the ‘b’ is ignored (via boolean short-circuiting).
false && 'a' evaluates to
false, so Ruby moves on, and returns ‘b’.
This is a lot like the
a ||= 'a' trick, which expands to
a = a || 'a', giving the variable a default value, if it’s not already initialized.
If Ruby already has the ternary operator, why bother? Personally, I find this form more natural (which surprised me, after years of using the ternary operator in Java and C#). For some reason, it reads more like natural language to me.
user_name = (user.authenticated? && user.name) || 'guest'
Does anyone else see it?