Ruby: Repeating a Method Multiple Times and Collecting Results in an Array

Question

I have a method that returns a hash. I want to repeat through this method five times, collecting the results into an array. Right now, I'm trying it like this:

votes = 5.times.collect{ create_vote }.inject{|memo, vote| memo << vote}

This doesn't work, and I believe it's failing because memo isn't an array. Is there another approach I could take to this problem?

Serabe · Accepted Answer · 2013-01-16 22:25:47Z

5

Yes:

votes = 5.times.collect { create_vote }

More generally, use each_with_object:

votes = 5.times.collect { create_vote }.each_with_object([]) {|o,memo| memo << o }

each_with_object is a method added because Ruby Core found that using inject in the way you intended to use it was very common.

answered Jan 16, 2013 at 22:25

Serabe

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2 Comments

steenslag Over a year ago

inject([]){|memo, vote| memo << vote} is fine (because memo<<vote returns memo). But when memo is a hash and you do something like memo[vote]=true in the block, it stops working (because it returns true, not memo). That's when each_with_object comes in handy.

Serabe Over a year ago

Indeed, but your intentions are clearer if you use the right method.

Daniel Evans · Accepted Answer · 2013-01-16 22:39:03Z

3

Use #map on a range instead of #times on a fixnum

(0..5).map { create_vote }

Or, map an array from the times

5.times.map { create_vote }

Each will give you an array with 5 elements.

answered Jan 16, 2013 at 22:39

Daniel Evans

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Comments

patrickmcgraw · Accepted Answer · 2013-01-16 22:24:46Z

1

How about:

votes = (1..5).collect { create_vote }

answered Jan 16, 2013 at 22:24

patrickmcgraw

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Avi Flax · Accepted Answer · 2016-07-18 23:46:15Z

0

I tried using the accepted answer, but then Rubocop told me that it would be faster to use Array.new as in:

votes = Array.new(5) { create_vote }

answered Jul 18, 2016 at 23:46

Avi Flax

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