iOS NSDecimalNumber的一些简单理解和使用

遇到一个问题 服务器返回货币数据 妈的 用string 》 floatvalue 不准确

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 翻译出来是个圆 吗的垃圾百度翻译

    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 = [NSDecimalNumber decimalNumberWithString:@"90.7049"];

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



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

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

NSDecimalNumber 其他用法

所有NSDecimalNumber对象是不可变的，这意味着已经被创建后不能改变它们的值。

NSDecimalNumber*price;

price = [NSDecimalNumber decimalNumberWithMantissa:1599

                                          exponent:-2   ／／10的－2次方

                                          isNegative:NO];

等效

price = [NSDecimalNumber decimalNumberWithString:@"15.99"];





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

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

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

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

NSDecimalNumber*numProducts = [NSDecimalNumber decimalNumberWithString:@"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];



subtotal的NSLog（@“小计：％@”，price1加price2后）;/ / 45.98

 afterCoupon的NSLog（@“subtotal优惠券后：％@”，subtotal减coupon）;/ / 40.98

 afterDiscount的NSLog（（@“折后：％@”），9/10）;/ / 36.882

 average的NSLog（@“每股平均价产品：％@”，平均）;/ / 18.441

 averageSquared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 = [NSDecimalNumber decimalNumberWithString:@"40.98"];

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



NSDecimalNumber*total = [subtotal decimalNumberByMultiplyingBy:discount

                                                   withBehavior:roundUp];

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



//比较大小

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

NSDecimalNumber*discount2 = [NSDecimalNumber decimalNumberWithString:@".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");

}

以上只是简单的使用介绍不足之处请大家指正，共同学习进步，谢谢。