CODEWITHSUNDEEP
ruby-on-railsrubyrandomruby-2.3
Fellow Stranger
Fellow Stranger

Reputation: 34013

Generate random number, the same every time

I have collections of items (ActiveRecord_AssociationRelation).

I need to randomly pick one item from each collection, but it should pick the same item the second and third time etc.

I'm thinking of some kind of one way algorithm, like hashing. E.g. perhaps based on the length of the collection, let's say 50, it will always generate the number 34.

Any idea how I could accomplish this?

Upvotes: 0

Views: 836

Answers (1)

steenslag
steenslag

Reputation: 80065

The Array samplemethod takes a Random Number Generator as a (named) argument, so you can do:

rng = Random.new(8) # The seed (8) is just a meaningles number.
a = ("a".."z").to_a
p a.sample(random: rng) # "d"
p a.sample(random: rng) # "u"

The next time it will result in "d" and "u" again.

If a repeatable random sequence is needed, all you need is a seeded Random number generator

rng2 = Random.new(10)
num = rng2.rand(collection.size)

Upvotes: 4

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