My app uses random numbers. I would like to seed the random number generator so that it won't be the same every time. How might I go about doing this?
EDIT:
What parameter do I give srand() to seed the random generator with the current time?
5
- Are you asking how to generate a random number in swift?JSA986– JSA9862014-09-17 16:25:56 +00:00Commented Sep 17, 2014 at 16:25
- no, just asking how to seed the rand() generatorquemeful– quemeful2014-09-17 16:30:41 +00:00Commented Sep 17, 2014 at 16:30
- stackoverflow.com/questions/24007129/…JSA986– JSA9862014-09-17 16:32:16 +00:00Commented Sep 17, 2014 at 16:32
- possible duplicate of Using srand(time(NULL)) in swift gives compiler errorMartin R– Martin R2014-09-17 16:55:12 +00:00Commented Sep 17, 2014 at 16:55
- 3The recommended way of generating random numbers is arc4random_uniform(), which doesn't need to be seeded.Atomix– Atomix2014-09-17 17:13:10 +00:00Commented Sep 17, 2014 at 17:13
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1 Answer
This works:
let time = UInt32(NSDate().timeIntervalSinceReferenceDate) srand(time) print("Random number: \(rand()%10)") 
6 Comments
obey
is there a way to seed with text and get number as result?
Ash
There are lots. One way would be to get the string's unicodeScalars value, iterate over each item in the collection reading its
value attribute, and perform some kind of mathematical operation to combine them all into one number. You could just add them all together, but that would mean that anagrams of the same string would have the same seed value - play around with it and I'm sure you can come up with a reasonable solution.
J.Doe
Will that value (NSDate().timeIntervalSinceReferenceDate) ever get too big to fit into a UInt32?
endavid
Notice that srand can't be used in Swift3 anymore. You can use srand48 instead.
Raphael
srandom() and random() seem to be preferable. |