I just had a quick question regarding loops in Ruby. Is there a difference between these two ways of iterating through a collection?
# way 1
@collection.each do |item|
# do whatever
end
# way 2
for item in @collection
# do whatever
end
Just wondering if these are exactly the same or if maybe there's a subtle difference (possibly when @collection
is nil).
This is the only difference:
each:
irb> [1,2,3].each { |x| }
=> [1, 2, 3]
irb> x
NameError: undefined local variable or method `x' for main:Object
from (irb):2
from :0
for:
irb> for x in [1,2,3]; end
=> [1, 2, 3]
irb> x
=> 3
With the for
loop, the iterator variable still lives after the block is done. With the each
loop, it doesn't, unless it was already defined as a local variable before the loop started.
Other than that, for
is just syntax sugar for the each
method.
When @collection
is nil
both loops throw an exception:
Exception: undefined local variable or method `@collection' for main:Object