ruby: What's the meaning of keyword "in"

Question

When I find the keyword "in" in ruby first time. I think maybe I can do that: 1 in (0..10) But it look like I cannot use it like that way.

Then I search it in ruby-lang.org, and google it. There is no answer!

What's the meaning of keyword "in" in ruby?

Answer 1

according to the pragmatic programmers book you se it as following

while *name*[, *name*]... in *expression* [do | :]
  body
end

so you use it in loops, sorry if this is vague, but i have only started learning ruby.

Answer 2

You should be able to do the following:

for i in 0..10 do
  puts i
end

The expression 1 in (0..10) that you mention won't work because a constant (1) can't vary over a range - it's a constant! You need to name a variable before the in keyword.

Hope that helps.

See this page as well.

Answer 3

In is also used inside of a conditions statement "pure sql"

Thing.find(:all, :conditions => ['id IN ?', somearray])