在iOS开发中，经常遇到和货币价格计算相关的，这时就需要注意计算精度的问题。使用float类型运算，经常出现误差。为了解决这种问题我们使用NSDecimalNumber，下面将通过例子的形式给大家展示一下。

1.加法的运算

//方式1：不进行四舍五入self.number1 = [NSDecimalNumber decimalNumberWithString:[NSString stringWithFormat:@"%f",3.155]]; self.number2 = [NSDecimalNumber decimalNumberWithString:[NSString stringWithFormat:@"%f",6.1]]; NSDecimalNumber *num = [self.number2 decimalNumberByAdding:self.number1]; NSLog(@"num===%@",num); //方式2：进行四舍五入 NSRoundUp属性使所有的操作算到最近的位置,其他的进位选项是NSRoundPlain, NSRoundDown, 和 NSRoundBankers,它们都被定义在NSRoundingMode,scale参数定义了结果值保留的小数位的数量,其余的参数给所有的操作定义了异常处理行为. //scale四舍五入，舍入位数 NSDecimalNumberHandler *roundUp = [NSDecimalNumberHandler decimalNumberHandlerWithRoundingMode:NSRoundPlain scale:2 raiseOnExactness:NO raiseOnOverflow:NO raiseOnUnderflow:NO raiseOnDivideByZero:YES]; NSDecimalNumber *num = [self.number2 decimalNumberByAdding:self.number1 withBehavior:roundUp]; NSLog(@"num===%@",num);

2.减法运算

//方式1：不进行四舍五入self.number1 = [NSDecimalNumber decimalNumberWithString:[NSString stringWithFormat:@"%f",10.1543]]; self.number2 = [NSDecimalNumber decimalNumberWithString:[NSString stringWithFormat:@"%f",2.3]]; NSDecimalNumber *num = [self.number1 decimalNumberBySubtracting:self.number2]; NSLog(@"num===%@",num); //方式2：进行四舍五入 NSDecimalNumberHandler *handler = [NSDecimalNumberHandler decimalNumberHandlerWithRoundingMode:NSRoundPlain scale:2 raiseOnExactness:NO raiseOnOverflow:NO raiseOnUnderflow:NO raiseOnDivideByZero:YES]; NSDecimalNumber *num = [self.number1 decimalNumberBySubtracting:self.number2 withBehavior:handler]; NSLog(@"num===%@",num);

3.乘法的运算

//方式1：不进行四舍五入self.number1 = [NSDecimalNumber decimalNumberWithString:[NSString stringWithFormat:@"%f",10.001]]; self.number2 = [NSDecimalNumber decimalNumberWithString:[NSString stringWithFormat:@"%d",2]]; NSDecimalNumber *num = [self.number1 decimalNumberByMultiplyingBy:self.number2]; NSLog(@"num===%@",num); //方式2：进行四舍五入 NSDecimalNumberHandler *handler = [NSDecimalNumberHandler decimalNumberHandlerWithRoundingMode:NSRoundPlain scale:2 raiseOnExactness:NO raiseOnOverflow:NO raiseOnUnderflow:NO raiseOnDivideByZero:YES]; NSDecimalNumber *num = [self.number1 decimalNumberByMultiplyingBy:self.number2 withBehavior:handler]; NSLog(@"num===%@",num);

4.除法的运算

//方式1：不进行四舍五入self.number1 = [NSDecimalNumber decimalNumberWithString:[NSString stringWithFormat:@"%f",10.14]]; self.number2 = [NSDecimalNumber decimalNumberWithString:[NSString stringWithFormat:@"%d",2]]; NSDecimalNumber *num = [self.number1 decimalNumberByDividingBy:self.number2]; NSLog(@"num===%@",num); //方式2：进行四舍五入 NSDecimalNumberHandler *handler = [NSDecimalNumberHandler decimalNumberHandlerWithRoundingMode:NSRoundPlain scale:1 raiseOnExactness:NO raiseOnOverflow:NO raiseOnUnderflow:NO raiseOnDivideByZero:YES]; NSDecimalNumber *num = [self.number1 decimalNumberByDividingBy:self.number2 withBehavior:handler]; NSLog(@"num===%@",num);

5.比较

self.number1 = [NSDecimalNumber decimalNumberWithString:[NSString stringWithFormat:@"%d",2]]; self.number2 = [NSDecimalNumber decimalNumberWithString:[NSString stringWithFormat:@"%d",2]]; //self.number1 < self.number2 if ([self.number1 compare:self.number2] == NSOrderedAscending) { NSLog(@"self.number1 < self.number2"); }else if([self.number1 compare:self.number2] ==NSOrderedDescending){ //self.number1 > self.number2 NSLog(@"self.number1 > self.number2"); }else if ([self.number1 compare:self.number2] == NSOrderedSame){ //self.number1 = self.number2 NSLog(@"self.number1 = self.number2"); }

6.指数运算

//方式1：不进行四舍五入self.number1 = [NSDecimalNumber decimalNumberWithString:[NSString stringWithFormat:@"%d",2]]; NSDecimalNumber *num = [self.number1 decimalNumberByMultiplyingByPowerOf10:2]; //方式2：进行四舍五入 NSDecimalNumberHandler *handler = [NSDecimalNumberHandler decimalNumberHandlerWithRoundingMode:NSRoundPlain scale:2 raiseOnExactness:NO raiseOnOverflow:NO raiseOnUnderflow:NO raiseOnDivideByZero:YES]; NSDecimalNumber *num = [self.number1 decimalNumberByMultiplyingByPowerOf10:2 withBehavior:handler]; NSLog(@"~~~%@",num);

7.次方运算

//方式1：进行四舍五入self.number1 = [NSDecimalNumber decimalNumberWithString:[NSString stringWithFormat:@"%d",2]]; NSDecimalNumber *num = [self.number1 decimalNumberByRaisingToPower:2]; //方式2：进行四舍五入 NSDecimalNumberHandler *handler = [NSDecimalNumberHandler decimalNumberHandlerWithRoundingMode:NSRoundPlain scale:2 raiseOnExactness:NO raiseOnOverflow:NO raiseOnUnderflow:NO raiseOnDivideByZero:YES]; NSDecimalNumber *num = [self.number1 decimalNumberByRaisingToPower:4 withBehavior:handler]; NSLog(@"~~~%@",num);