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从 NSArray 中随机选择一个 objectAtIndex

发布于 2024-12-12 10:50:56 字数 141 浏览 0 评论 0原文

我有一个 NSArray，其中包含索引 0 - 9 的 10 个对象。数组中的每个条目都是一个引号。

当我的用户选择“随机引用”选项时，我希望能够从数组中选择一个随机条目并显示该条目中包含的文本。

谁能指出我如何实现这一目标的正确方向？

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堇年纸鸢 2024-12-19 10:50:56

我建议您使用它而不是硬编码 10;这样，如果您添加更多报价，它会自动计算出来，而无需更改该数字。

NSInteger randomIndex = arc4random()%[array count];
NSString *quote = [array objectAtIndex:randomIndex];

I'd recommend you use this instead of hardcoding the 10; that way, if you add more quotations, it will work it out automatically, without you needing to change that number.

NSInteger randomIndex = arc4random()%[array count];
NSString *quote = [array objectAtIndex:randomIndex];

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也只是曾经 2024-12-19 10:50:56

您可能想要使用 arc4random() 从 0-9 中选择一个对象。然后，只需

NSString* string = [array objectAtIndex:randomPicked];

获取条目的文本即可。

Your probably going to want to use arc4random() to pick an object from 0-9. Then, simply do

NSString* string = [array objectAtIndex:randomPicked];

to get the text of the entry.

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溺渁∝ 2024-12-19 10:50:56

您可以使用arc4random()%10来获取索引。存在轻微的偏差，这应该不是问题。

最好使用arc4random_uniform(10)，没有偏差，而且更容易使用。

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你是暖光i 2024-12-19 10:50:56

首先，在边界之间获取一个随机数，请参阅此讨论和相关的手册页。然后用它索引到数组中。

int random_number = rand()%10; // Or whatever other method.
return [quote_array objectAtIndex:random_number];

编辑：对于那些无法从链接正确插入或只是不想阅读建议参考文献的人，让我为您说明一下：

// Somewhere it'll be included when necessary, 
// probably the header for whatever uses it most.
#ifdef DEBUG 
#define RAND(N) (rand()%N)
#else 
#define RAND(N) (arc4random()%N)
#endif

...

// Somewhere it'll be called before RAND(), 
// either appDidLaunch:... in your application delegate 
// or the init method of whatever needs it.
#ifdef DEBUG
// Use the same seed for debugging 
// or you can get errors you have a hard time reproducing.
srand(42);
#else
// Don't seed arc4random()
#endif

....

// Wherever you need this.
NSString *getRandomString(NSArray *array) {
    #ifdef DEBUG
    // I highly suggest this, 
    // but if you don't want to put it in you don't have to.
    assert(array != nil);
    #endif
    int index = RAND([array count]);
    return [array objectAtIndex:index];
}

First, get a random number between your bounds, see this discussion and the relevant man pages. Then just index into the array with it.

int random_number = rand()%10; // Or whatever other method.
return [quote_array objectAtIndex:random_number];

Edit: for those who can't properly interpolate from the links or just don't care to read suggested references, let me spell this out for you:

// Somewhere it'll be included when necessary, 
// probably the header for whatever uses it most.
#ifdef DEBUG 
#define RAND(N) (rand()%N)
#else 
#define RAND(N) (arc4random()%N)
#endif

...

// Somewhere it'll be called before RAND(), 
// either appDidLaunch:... in your application delegate 
// or the init method of whatever needs it.
#ifdef DEBUG
// Use the same seed for debugging 
// or you can get errors you have a hard time reproducing.
srand(42);
#else
// Don't seed arc4random()
#endif

....

// Wherever you need this.
NSString *getRandomString(NSArray *array) {
    #ifdef DEBUG
    // I highly suggest this, 
    // but if you don't want to put it in you don't have to.
    assert(array != nil);
    #endif
    int index = RAND([array count]);
    return [array objectAtIndex:index];
}

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~没有更多了~