遇到的問題,從伺服器拿的資料NSString型別的,然後轉化成CGFloat型別的,資料的值就不準確了,沒辦法,就找了下資料,找到了蘋果有專門的API,針對金融貨幣單位,希望可以解決有遇到同樣問題的人.

NSDecimalNumberHandler *roundUp = [NSDecimalNumberHandler

                                       decimalNumberHandlerWithRoundingMode:NSRoundBankers

                                       scale:2

                                       raiseOnExactness:NO

                                       raiseOnOverflow:NO

                                       raiseOnUnderflow:NO

                                       raiseOnDivideByZero:YES];

列舉

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

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

    NSRoundUp,      // Always up    ／／ 只入不捨

    NSRoundBankers  // on a tie round so last digit is even  貌似四捨五入

    //90.7049+0.22 然後四捨五入

    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（@“小計：％@”，加）;/ / 45.98

 的NSLog（@“優惠券後：％@”，減）;/ / 40.98

 的NSLog（（@“折後：％@”），乘）;/ / 36.882

 的NSLog（@“每股平均價產品：％@”，平均）;/ / 18.441

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

//保留小數點後兩位

NSDecimalNumberHandler*roundUp = [NSDecimalNumberHandler

                                   decimalNumberHandlerWithRoundingMode:NSRoundUp

                                   scale:2

                                   raiseOnExactness:NO

                                   raiseOnOverflow:NO

                                   raiseOnUnderflow:NO

                                   raiseOnDivideByZero:YES];

//9折後 36.882 有餘進位結果 36.89

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

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

NSDecimalNumber*total = [subtotal decimalNumberByMultiplyingBy:discount

                                                   withBehavior:roundUp];

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

//比較大小

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

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

NSComparisonResult result = [discount1 compare:discount2];

if (result ==NSOrderedAscending) {

    NSLog(@"85%% < 90%%小於");

} else if (result == NSOrderedSame) {

    NSLog(@"85%% == 90%%等於");

} elseif (result ==NSOrderedDescending) {

    NSLog(@"85%% > 90%%大於");

}