arc4random:限制生成的随机数的值

Question

构建了一个iPhone应用程序,当按下按钮时,该应用程序会为标签生成随机数.

它运行正常,但我放的任何值似乎都不限制生成的随机数的值.它始终是9位数.

-(IBAction)genRandnum:(id)sender {

    NSNumber *randomNumber = [NSNumber numberWithInt: (arc4random() % 5) + 1];

    NSNumber *randomLabeltxt = [[NSString alloc] initWithFormat:@"It worked!", randomNumber];
    randLabel.text = [NSString stringWithFormat: @"%d", randomLabeltxt];
    [randomLabeltxt release];
}

正如你所看到的,我在%符号后面放了5个,但它产生了9位数字.

Answer 1

1. NSNumber是一个Objective-C对象,因此您应该使用%@它来显示它.%d显示一个9位数字,因为它是该NSNumber的地址.

2. NSString与NSNumber不同.

正确和简化的代码应如下所示:

int randomNumber = (arc4random() % 5) + 1;
// no need to create an NSNumber if you do not need to store it into an NS container.

randLabel.text = [NSString stringWithFormat:@"It worked! %d", randomNumber];
// no need to create an intermediate NSString variable.
//  you can directly assign the string to the label's text.