I am following a tutorial.
arr = [["cow", "moo"], ["duck", "quack"]]
bucket = arr[0]
bucket.each_with_index do |kv, i|
k, v = kv
puts k
puts v
end
I understand that when it goes through arr[0], it is first kv = cow and i = 0, and then kv = moo and i = 1. How does k, v = kv make sense? To me, it seems that k = kv and v = kv, but that isn't the case. I don't understand the purpose.
Basically the line k, v = kv means that you are assigning kv to k or k= kv
comma separated assignment is just another way of assigning multiple variables in one line, it's just syntactic sugar.
Try messing around with your code and do something like this for example:
arr = [["cow", "moo"], ["duck", "quack"]]
bucket = arr[0]
bucket.each_with_index do |kv, i|
k, v = kv, i
puts "k is #{k} and v is #{v}"
end
# k is cow and v is 0
# k is moo and v is 1
each_with_index do |(k, v), i| avoids having to add the break-out line.
def Dict.get_slot on the page|(k,v),i| it's the first time I see someone doing that :)v. So it isn't actually nil when it's running. I just don't get why.What's happening here is it's breaking out the key/value pair variable kv into two separate variables k and v. You'll need to adjust your code to look like this:
arr = [["cow", "moo"], ["duck", "quack"]]
arr.each_with_index do |kv, i|
k, v = kv
puts k
puts v
end
What's happening here is demonstrated by this:
kv = [ :key, :value ]
# Assign k to the first value, v to the second in kv
k, v = kv
k
# => :key
v
# => :value
A less messy way of doing this break-out is this:
arr.each_with_index do |(k, v), i|
# ... Use k and v normally
end
That notation allows you to expand the array into separate variables in advance of using them. It's a trick that comes in handy when dealing with value pairs of this sort.
It's worth noting you wouldn't have to do this if you didn't use each_with_index, as each is sufficient here since that index value is never used:
each do |k, v|
# ...
end
bucket is. It is different from arr.
k = kvandv = kv.arr.each_with_index ....get_in the method name.