Don't prefer Array.new(3) over 3.times.map

[lewispb]

Context https://github.com/cookpad/global-web/pull/7808#issuecomment-387919152

Disable https://www.rubydoc.info/gems/rubocop/RuboCop/Cop/Performance/TimesMap

I prefer the readability of 3.times.map { |x| } over Array.new(3).map { |x| }.

More discussion:
https://stackoverflow.com/questions/41518896/why-does-rubocop-suggest-replacing-times-map-with-array-new

[karlentwistle]

I agree

[errm]

Without taking a view here the reason for this cop existing is because the Array.new form is more performant (apparently)

See: rubocop/rubocop#2583

I personally think that unless you are specifically optimising some code for performance you should always use the more readable form anyway ....

[balvig]

Great, thanks a lot! 👍

[Knack]

I prefer the readability of 3.times.map { |x| } over Array.new(3).map { |x| }.

Well, it's really Array.new(3) { |x| }

I personally don't see any difference in readability. I would even say that I prefer the second: "Create an new array of size 3 and initialize it using the block"

instead of "map "3.times" with a block"

[balvig]

@Knack now sure if this convinces you but I found the original diff was easier to follow that way.

"Give me this thing 3 times"

[lewispb]

@Knack sorry my mistake on the syntax.

[Knack]

I found the original diff was easier to follow that way.

But that's because the original code had a bug

Array.new(3).map {} means "Create an empty array and use it to map another array"

Whereas

Array.new(3) {} means "Create an array of size 3 and initialize it". Much simpler, IMHO.

Even if all the values are the same you can pass it as a second argument: Array.new(3, "x")

But as I said, I don't see a big difference and I don't care too much about performance. So it's ok to disable it.

Either one seems good

[l15n]

Agree about the lack of need to optimize for performance here. I think I'd also fall into the habit of writing 3.times.map { }, but I'm convinced by Paco that Array.new(3) { } conveys the intent better.

[balvig]

Thanks for the extra explanation @Knack!

I also agree with this quote:

Either one seems good

In the end I think the PR title is maybe incorrect, but the fix is 👍 😉

[Knack]

Yes, it would be more appropriate "Don't prefer Array.new(3) over 3.times.map" 😄

[lewispb]

Thanks for the suggestion @Knack I have changed it.