IOS 关于四舍五入的神器--NSDecimalNumber

如何只舍不入。比如 float price = 0.126，怎么样才能得到0.12？

当然，通过字符串截取的办法肯定也能达到相同的效果。但是就是这么一个简单的问题要通过一些判断和截取才能获得结果，总感觉有点笨拙。

下面先给出该问题的解决办法：

 

-(NSString *)notRounding:(float)price afterPoint:(int)position{

    NSDecimalNumberHandler* roundingBehavior = [NSDecimalNumberHandler decimalNumberHandlerWithRoundingMode:NSRoundDown scale:position raiseOnExactness:NO raiseOnOverflow:NO raiseOnUnderflow:NO raiseOnDivideByZero:NO];

    NSDecimalNumber *ouncesDecimal;

    NSDecimalNumber *roundedOunces;

    

    ouncesDecimal = [[NSDecimalNumber alloc] initWithFloat:price];

    roundedOunces = [ouncesDecimal decimalNumberByRoundingAccordingToBehavior:roundingBehavior];

    [ouncesDecimal release];

    return [NSString stringWithFormat:@"%@",roundedOunces];

}

介绍一下参数：

price:需要处理的数字，

position：保留小数点第几位，

然后调用

 

    float s =0.126;

    NSString *sv = [self notRounding:s afterPoint:2];

    NSLog(@"sv = %@",sv);

输出结果为：sv = 0.12

 

接下来介绍NSDecimalNumberHandler初始化时的关键参数：decimalNumberHandlerWithRoundingMode：NSRoundDown，

NSRoundDown代表的就是 只舍不入。

scale的参数position代表保留小数点后几位。

 

如果只入不舍怎么办，比如，float 0.162 想要得到0.17该怎么做？，在开发文档上有这样一个表，是按照保留小数点后一位处理的。相信大家一看就明白了：

 

方法二:

1、round(12345.6789) 结果为：12346

2、round(12345.6789*100)/100 结果为：12345.68

第二个是我要的结果，但是我不明白这么个简单的四舍五入要搞的这么复杂，应该有更好的吧，我记得在其他语言里用：round(12345.6789，2) 就可以实现四舍五入到两位小数。

 

 

方法三:

NSTimeInterval Interval = 305.721125;

 

NSInteger timeInt = [[NSString stringWithFormat:@"%.0f", Interval] integerValue];

 

 

 

Interval:305.721125

 

timeInt:306

1 NSLog(@"%@", [NSString stringWithFormat:@"%.0f", 1.0003]);
2 NSLog(@"%@", [NSString stringWithFormat:@"%.0f", 1.9003]);
3 NSLog(@"%@", [NSString stringWithFormat:@"%.0f", 1.5003]);
4 NSLog(@"%@", [NSString stringWithFormat:@"%.0f", 1.4003]);

1  1

1 1

1 2

1 2

1 1   方法四: 　　 1. /     //Test "/"    cout << "Test \"/\"!" << endl;    cout << "7   / 2   = " << 7/2 << endl;      //3    cout << "7   / 2.0 = " << 7/2.0 << endl;    //3.5    cout << "7.0 / 2   = " << 7.0/2 << endl;    //3.5    cout << "7.0 / 2.0 = " << 7.0/2.0 << endl; //3.5    cout << "7   / 3   = " << 7/3 << endl;      //2    cout << endl;2. %    //Test "%"    cout << "Test \"%\"!" << endl;    cout << "9   % 3   = " << 9%3 << endl;      //0    cout << "9   % 4   = " << 9%4 << endl;      //1    //cout << "9.0 % 3   = " << 9.0%3 << endl;    //cout << "9   % 3.0 = " << 9%3.0 << endl;    cout << endl;3. 四舍五入    //Test round()    cout << "Test \"四舍五入\"!" << endl;    double dRoundA = 1.4;    double dRoundB = 1.6;    double dRoundLowA = -1.4;    double dRoundLowB = -1.6;    double dRoundLowC = 0.0;    cout << dRoundA << " = " << RoundEx(dRoundA) << endl;         //1    cout << dRoundB << " = " << RoundEx(dRoundB) << endl;         //2    cout << dRoundLowA << " = " << RoundEx(dRoundLowA) << endl;   //-1    cout << dRoundLowB << " = " << RoundEx(dRoundLowB) << endl;   //-2    cout << dRoundLowC << " = " << RoundEx(dRoundLowC) << endl;   //0    cout << endl;double RoundEx(const double& dInput){    double dIn = dInput;    if (dInput >= 0.0)    //???    {        return int(dIn + 0.5);    }     else    {        return int(dIn - 0.5);    }}4. ceil() 向上取整    //Test ceil() 向上取整    cout << "Test ceil() 向上取整!" << endl;     cout << "ceil 1.2 = " << ceil(1.2) << endl;      //2    cout << "ceil 1.8 = " << ceil(1.8) << endl;      //2    cout << "ceil -1.2 = " << ceil(-1.2) << endl;    //-1    cout << "ceil -1.8 = " << ceil(-1.8) << endl;    //-1    cout << "ceil 0.0 = " << ceil(0.0) << endl;      //0    cout << endl;5. floor() 向下取整    //Test floor() 向下取整    cout << "Test floor() 向下取整!" << endl;    cout << "floor 1.2 = " << floor(1.2) << endl;    //1    cout << "floor 1.8 = " << floor(1.8) << endl;    //1    cout << "floor -1.2 = " << floor(-1.2) << endl; //-2    cout << "floor -1.8 = " << floor(-1.8) << endl; //-2    cout << "floor 0.0 = " << floor(0.0) << endl;    //0    cout << endl;