ios - 使用 arc4random 的更好方法

Question

我有一个随机方法来创建 2 个随机整数。我担心的是 %65-%70 的输出是相同的整数，例如“5-5”“4-4”“3-3”。

-(void)random{
NSUInteger randomNumber = arc4random_uniform(5);

    switch (randomNumber) {
        case 0:
            _tile2.image = [UIImage imageNamed:@"one.png"];
            break;

        case 1:
            _tile2.image = [UIImage imageNamed:@"two.png"];
            break;

        case 2:
            _tile2.image = [UIImage imageNamed:@"three.png"];
            break;

        case 3:
            _tile2.image = [UIImage imageNamed:@"four.png"];
            break;

        case 4:
            _tile2.image = [UIImage imageNamed:@"five.png"];
            break;
    }

    NSUInteger randomNumber2 = arc4random_uniform(5);

    switch (randomNumber2) {
        case 0:
            _tile3.image = [UIImage imageNamed:@"one.png"];
            break;

        case 1:
            _tile3.image = [UIImage imageNamed:@"two.png"];
            break;

        case 2:
            _tile3.image = [UIImage imageNamed:@"three.png"];
            break;

        case 3:
            _tile3.image = [UIImage imageNamed:@"four.png"];
            break;

        case 4:
            _tile3.image = [UIImage imageNamed:@"five.png"];
            break;
    }
}

我应该创建 25 个不同的案例以获得更好的结果吗？

NSUInteger randomNumber = arc4random_uniform(25);

   switch (randomNumber) {
        case 0:
            _tile2.image = [UIImage imageNamed:@"one.png"];
            _tile3.image = [UIImage imageNamed:@"one.png"];
            break;

        case 1:
            _tile2.image = [UIImage imageNamed:@"one.png"];
            _tile3.image = [UIImage imageNamed:@"two.png"];
            break;

        case 2:
            _tile2.image = [UIImage imageNamed:@"one.png"];
            _tile3.image = [UIImage imageNamed:@"three.png"];
            break;

        case 3:
            _tile2.image = [UIImage imageNamed:@"one.png"];
            _tile3.image = [UIImage imageNamed:@"four.png"];
            break;

        case 4:
            _tile2.image = [UIImage imageNamed:@"one.png"];
            _tile3.image = [UIImage imageNamed:@"five.png"];
            break;

        case 5:
            _tile2.image = [UIImage imageNamed:@"two.png"];
            _tile3.image = [UIImage imageNamed:@"one.png"];
            break;

        ...
    }
}

arc4random_uniform 非常适合获取一个随机整数。当我需要获得 2 个或更多随机数时，输出并不是那么好。这样做的最佳方法是什么？

Answer 1

对不起，我不相信你。你一定在做一些与你所展示的不同的事情。粘贴到 Playground 中的以下代码始终给出 20% 左右的匹配度，而不是您声称的 65-70%:

import Cocoa

let sampleSize = 1000
var count = 0
for i in 1...sampleSize {
  var randomNumber1 = arc4random_uniform(5)
  var randomNumber2 = arc4random_uniform(5)
  if randomNumber1 == randomNumber2 {
    ++count
  }
}
println( Double(count) / Double(sampleSize) )

无论您遇到什么问题，都与 arc4random_uniform 如何生成值对无关。