Objective-C: Get random number 擷取随機數

轉載自：http://hi.baidu.com/bunsman/blog/item/9c7cf79ba2261cacc9eaf4e4.html

參考：http://www.friendlydeveloper.com/2010/02/objective-c-get-random-number/comment-page-1/

-(int)getRandomNumber:(int)from to:(int)to {

return(int)(from + arc4random() % (to-from+1));

}

How to use:

Implement method above into your .m file

Add the following line to your .hfile:

1)

-(int)getRandomNumber:(int)from to:(int)to;

2) Call the method like:

intrandomNumber = [selfgetRandomNumber:9to:99];

//this gets you a random number between 9 and 99

關于生成多個不重複随機數的問題。

我的解決思路是，先建立一個MutableArray,放入随機數的取值範圍，然後從0到［mutableArray count］生成的随機數index，去取mutable的值。取一個然後再remove掉。就可以得到不重複的随機數了。

示例代碼：

//生成多個随機數

NSNumber*irandom1, *irandom2, *irandom3, *irandom4;

NSUIntegercapacity = [dataArraycount]-1;//dataArray是取值的源數組

NSMutableArray*container = [[NSMutableArrayalloc]initWithCapacity:capacity];

for(NSUIntegeri =0; i < [dataArraycount] ; i++) {

NSNumber*nsi = [NSNumbernumberWithInt:i];

[containeraddObject:nsi];

}

NSUIntegerindex = [setintValue];

[containerremoveObjectAtIndex:index];

index = (arc4random() % [containercount]);

irandom1 = [containerobjectAtIndex:index];

[containerremoveObjectAtIndex:index];

index = (arc4random() % [containercount]);

irandom2 = [containerobjectAtIndex:index];

[containerremoveObjectAtIndex:index];

index = (arc4random() % [containercount]);

irandom3 = [containerobjectAtIndex:index];

[containerremoveObjectAtIndex:index];

index = (arc4random() % [containercount]);

irandom4 = [containerobjectAtIndex:index];

[containerrelease];