在Objective-C中生成随机数 [英] Generating random numbers in Objective-C

问题描述

我主要是Java主管，我想要一种生成0到74之间的伪随机数的方法.在Java中，我将使用以下方法:

I'm a Java head mainly, and I want a way to generate a pseudo-random number between 0 and 74. In Java I would use the method:

Random.nextInt(74)

我对讨论种子或真正随机性的兴趣不大，而对您如何在Objective-C中完成相同任务不感兴趣.我曾搜寻过Google，但似乎有很多不同且相互冲突的信息.

I'm not interested in a discussion about seeds or true randomness, just how you accomplish the same task in Objective-C. I've scoured Google, and there just seems to be lots of different and conflicting bits of information.

推荐答案

您应该使用arc4random_uniform()函数.它使用优于rand的算法.您甚至不需要设置种子.

You should use the arc4random_uniform() function. It uses a superior algorithm to rand. You don't even need to set a seed.

#include <stdlib.h>
// ...
// ...
int r = arc4random_uniform(74);

arc4random手册页:

NAME
     arc4random, arc4random_stir, arc4random_addrandom -- arc4 random number generator

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <stdlib.h>

     u_int32_t
     arc4random(void);

     void
     arc4random_stir(void);

     void
     arc4random_addrandom(unsigned char *dat, int datlen);

DESCRIPTION
     The arc4random() function uses the key stream generator employed by the arc4 cipher, which uses 8*8 8
     bit S-Boxes.  The S-Boxes can be in about (2**1700) states.  The arc4random() function returns pseudo-
     random numbers in the range of 0 to (2**32)-1, and therefore has twice the range of rand(3) and
     random(3).

     The arc4random_stir() function reads data from /dev/urandom and uses it to permute the S-Boxes via
     arc4random_addrandom().

     There is no need to call arc4random_stir() before using arc4random(), since arc4random() automatically
     initializes itself.

EXAMPLES
     The following produces a drop-in replacement for the traditional rand() and random() functions using
     arc4random():

           #define foo4random() (arc4random() % ((unsigned)RAND_MAX + 1))

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