iOS NSDecimalNumber精确数值计算以及小数点后精确保留2位数字

遇到的问题,从服务器拿的数据NSString类型的,然后转化成CGFloat类型的,数据的值就不准确了,没办法,就找了下资料,找到了苹果有专门的API,针对金融货币单位,希望可以解决有遇到同样问题的人.

NSDecimalNumberHandler *roundUp = [NSDecimalNumberHandler

                                       decimalNumberHandlerWithRoundingMode:NSRoundBankers

                                       scale:2

                                       raiseOnExactness:NO

                                       raiseOnOverflow:NO

                                       raiseOnUnderflow:NO

                                       raiseOnDivideByZero:YES];

枚举

    NSRoundPlain,   // Round up on a tie ／／貌似取整 

    NSRoundDown,    // Always down == truncate  ／／只舍不入

    NSRoundUp,      // Always up    ／／ 只入不舍

    NSRoundBankers  // on a tie round so last digit is even  貌似四舍五入

    

    //90.7049+0.22 然后四舍五入

    NSDecimalNumber *subtotal = [NSDecimalNumberdecimalNumberWithString:@"90.7049"];

    NSDecimalNumber *discount = [NSDecimalNumberdecimalNumberWithString:@"0.22"];

    

    NSDecimalNumber *total = [subtotal decimalNumberByAdding:discount withBehavior:roundUp];

    NSLog(@"Rounded total: %@", total);

     

NSDecimalNumber*price1 = [NSDecimalNumberdecimalNumberWithString:@"15.99"];

NSDecimalNumber*price2 = [NSDecimalNumberdecimalNumberWithString:@"29.99"];

NSDecimalNumber*coupon = [NSDecimalNumberdecimalNumberWithString:@"5.00"];

NSDecimalNumber*discount = [NSDecimalNumberdecimalNumberWithString:@".90"];

NSDecimalNumber*numProducts = [NSDecimalNumberdecimalNumberWithString:@"2.0"];

 

NSDecimalNumber *subtotal = [price1 decimalNumberByAdding:price2];

NSDecimalNumber *afterCoupon = [subtotal decimalNumberBySubtracting:coupon];

NSDecimalNumber *afterDiscount = [afterCoupon decimalNumberByMultiplyingBy:discount];

NSDecimalNumber *average = [afterDiscount decimalNumberByDividingBy:numProducts];

NSDecimalNumber*averageSquared = [average decimalNumberByRaisingToPower:2];

 

的NSLog（@“小计：％@”，加）;/ / 45.98

 的NSLog（@“优惠券后：％@”，减）;/ / 40.98

 的NSLog（（@“折后：％@”），乘）;/ / 36.882

 的NSLog（@“每股平均价产品：％@”，平均）;/ / 18.441

 的NSLog（@“平均价的平方：％@”，averageSquared）;/ / 340.070481

 

//保留小数点后两位

NSDecimalNumberHandler*roundUp = [NSDecimalNumberHandler

                                   decimalNumberHandlerWithRoundingMode:NSRoundUp

                                   scale:2

                                   raiseOnExactness:NO

                                   raiseOnOverflow:NO

                                   raiseOnUnderflow:NO

                                   raiseOnDivideByZero:YES];

 

//9折后 36.882 有余进位结果 36.89

NSDecimalNumber*subtotal = [NSDecimalNumberdecimalNumberWithString:@"40.98"];

NSDecimalNumber*discount = [NSDecimalNumberdecimalNumberWithString:@".90"];

 

NSDecimalNumber*total = [subtotal decimalNumberByMultiplyingBy:discount

                                                   withBehavior:roundUp];

NSLog(@"Rounded total: %@", total);

 

//比较大小

NSDecimalNumber*discount1 = [NSDecimalNumberdecimalNumberWithString:@".85"];

NSDecimalNumber*discount2 = [NSDecimalNumberdecimalNumberWithString:@".9"];

NSComparisonResult result = [discount1 compare:discount2];

if (result ==NSOrderedAscending) {

    NSLog(@"85%% < 90%%小于");

} else if (result == NSOrderedSame) {

    NSLog(@"85%% == 90%%等于");

} elseif (result ==NSOrderedDescending) {

    NSLog(@"85%% > 90%%大于");

}