It seems this doesn't work as expected:
if c = Countries.first.nil?
... do something
end
The comparison works but the assignment doesn't. Is there a way to do both the comparison and assignment in one line?
views:
61answers:
2
+5
A:
This is what you really want:
if (c = Countries.first).nil?
# ... do something
end
In your example, you will get c = (Countries.first.nil?), so c will be false or true.
You might actually write it like this:
unless (c = Countries.first)
# ... do something
end
but caution! I would keep the () in place, because otherwise it will appear like you meant comparison, and the ruby interpreter will warn you.
I use this pattern sometimes, but use it sparingly, because it makes things less clear.
Peter
2010-09-30 22:07:25
Why not as Reed had it? I assumed he wanted to assign c = true or false (from `.nil?`)... but I probably misread the intent of his question.
Andrew Vit
2010-09-30 22:13:27
@Andrew The way Reed has it will set `c` to `Countries.first.nil?`, but he wanted to actually set `c` to `Countries.first` and then check `if c.nil?`
Daniel Vandersluis
2010-09-30 22:15:10
This is a good example of why using parenthesis is important.
Greg
2010-10-01 00:29:24
Or a better example of how splitting a statement into two doesn't hurt.
Chubas
2010-10-01 03:43:32
+1
A:
If you want to assign c to Countries.first if c is nil:
c = Countries.first if c.nil?
bryanweatherly
2010-09-30 22:17:38
actually, if this is what you want you can just use `c ||= Countries.first`.
Peter
2010-09-30 22:18:27