NSDecimalNumber乘法奇怪 [英] NSDecimalNumber multiplication strangeness
本文介绍了NSDecimalNumber乘法奇怪的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
ExclusivePrice，quantity都是NSDecimalNumbers。
ExclusivePrice, quantity are both NSDecimalNumbers.
NSDecimalNumber *price = [exclusivePrice decimalNumberByMultiplyingBy:quantity];
NSLog(@"%@ * %@ = %@", exclusivePrice, quantity, price);
我得到的结果：
2010-04-05 00:22:29.111 TestApp[13269:207] 65 * 2 = -0.0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000007169919476068871316457914368
我的预期：
2010-04-05 00:22:29.111 TestApp[13269:207] 65 * 2 = 130
任何人都可以解释这个问题吗？
Can anyone explain this please?
编辑：
完整再现：
NSNumberFormatter *formatter = [[NSNumberFormatter alloc] init];
[formatter setNumberStyle:NSNumberFormatterDecimalStyle];
NSDecimalNumber *n2 = (NSDecimalNumber *)[formatter numberFromString:@"2"];
NSDecimalNumber *n1 = (NSDecimalNumber *)[NSDecimalNumber numberWithInt:65];
NSDecimalNumber *n3 = [n1 decimalNumberByMultiplyingBy:n2];
NSLog(@"%@ * %@ = %@", n1, n2, n3);
推荐答案
我发现答案：根据如何使用NSDecimalNumber？我不能轻易地在NSNumber和NSDecimalNumber之间转换。要从一个转换到另一个，我必须做：
I found the answer: According to How to use NSDecimalNumber? I can't easily convert between NSNumber and NSDecimalNumber. To convert from the one to the other I have to do :
NSDecimalNumber *n2 = [NSDecimalNumber decimalNumberWithDecimal:
[[formatter numberFromString:@"2"] decimalValue]];
如果NSNumberFormatter有一个decimalNumberFromString：方法，将会很好。
It would have been nice if the NSNumberFormatter had a decimalNumberFromString: method.
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