Destructuring assignment in block parameters

…which is just a fancy way to say that this works like I think it should:


>> [['foo', 1], ['bar', 2], ['honk', 1000]].partition { |str, val| val > 999 }
=> [[["honk", 1000]], [["foo", 1], ["bar", 2]]]

Which beats the pants off this:


>> [['foo', 1], ['bar', 2], ['honk', 1000]].partition do |pair|
?>     str, val = pair
>>     val > 999
>>   end
=> [[["honk", 1000]], [["foo", 1], ["bar", 2]]]

So, you see, the array elements get unpacked into @str@ and @val@ inside your block. Which is unexpected, but totally and thoroughly lovely. To my eyes, the former is much easier to read.

2 responses to “Destructuring assignment in block parameters”

Marcel Molina says:

May 23, 2008 at 3:42 PM

And if you have no use for one of the arguments passed to the block I tend to name the unused argument _.

For example:

name_to_age_mapping.partition do |_, age|
age > minimum_age
end
Adam Keys says:

May 23, 2008 at 3:44 PM

I found myself doing that a few months ago. Its so very Erlang-ish.