ruby-on-rails - 如何在Ruby中获得随机数(How to get a random number in Ruby)

Question

如何生成0到n之间的随机数？

  ask by Mark A. Nicolosi translate from so

Answer 1

Use rand(range)

(使用rand(range))

From Ruby Random Numbers :

(从Ruby随机数开始 ：)

If you needed a random integer to simulate a roll of a six-sided die, you'd use: 1 + rand(6) .

(如果您需要一个随机整数来模拟六面骰子的掷骰，则可以使用： 1 + rand(6) 。)

A roll in craps could be simulated with 2 + rand(6) + rand(6) .

(掷骰子可以用2 + rand(6) + rand(6)模拟。)

Finally, if you just need a random float, just call rand with no arguments.

(最后，如果您只需要随机浮点数，则可以不带任何参数调用rand 。)

---

As Marc-André Lafortune mentions in his answer below (go upvote it) , Ruby 1.9.2 has its own Random class (that Marc-André himself helped to debug , hence the 1.9.2 target for that feature).

(正如Marc-AndréLafortune在下面的回答中提到的（支持它） ， Ruby 1.9.2具有自己的Random类 （Marc-André自己进行了调试 ，因此该功能的目标1.9.2 ）。)

For instance, in this game where you need to guess 10 numbers , you can initialize them with:

(例如，在这个游戏中，您需要猜测10个数字 ，可以使用以下方法初始化它们：)

10.times.map{ 20 + Random.rand(11) } 
#=> [26, 26, 22, 20, 30, 26, 23, 23, 25, 22]

Note:

(注意：)

• Using Random.new.rand(20..30) (using Random.new ) generally would not be a good idea, as explained in detail (again) by Marc-André Lafortune , in his answer (again).

  (通常，使用Random.new.rand(20..30) （使用Random.new ）并不是一个好主意，正如Marc-AndréLafortune （再次）在其答案中再次详细解释的那样。)

• But if you don't use Random.new , then the class method rand only takes a max value, not a Range , as banister (energetically) points out in the comment (and as documented in the docs for Random ).

  (但是，如果您不使用Random.new ，则类方法rand仅采用一个max ，而不是Range ，因为banister （强烈地）在注释中指出了这一点（并在docs的文档中针对Random ）。)

  Only the instance method can take a Range , as illustrated by generate a random number with 7 digits .

  (只有实例方法可以采用Range ，如生成7位随机数所示。)

This is why the equivalent of Random.new.rand(20..30) would be 20 + Random.rand(11) , since Random.rand(int) returns “a random integer greater than or equal to zero and less than the argument .” 20..30 includes 30, I need to come up with a random number between 0 and 11, excluding 11.

(这就是为什么Random.new.rand(20..30)等于20 + Random.rand(11) ，因为Random.rand(int)返回“一个大于或等于0且小于 0的随机整数。 自变量 。” 20..30包括30，我需要给出一个介于0到11之间的随机数（不包括11）。)