iPhone：如何将货币符号的字符串转换为负数？

Question

说我有一个字符串是23.56英镑或23.56美元，我怎么能把它转换成-23.56？

我有这部分

NSMutableString *strAmount = [NSMutableString stringWithString:txtAmount.text]; 
[strAmount replaceCharactersInRange: [strAmount rangeOfString: strCurrencySymbol] withString:@""]; 

Answer 1

这看起来像一个良好的开端。尽管创建了一组货币符号后，您可以使用rangeOfCharacterFromSet:而不是rangeOfString:。您的代码看起来是这样的：

NSMutableString *strAmount = [NSMutableString stringWithString:txtAmount.text]; 
NSCharacterSet *currencySet = [NSCharacterSet characterSetWithCharactersInString:@"$€£"]; 
[strAmount replaceCharactersInRange: [strAmount rangeOfCharacterFromSet:currencySet] withString:@"-"]; 

Answer 2

使用NSNumberFormatter

NSNumberFormatter *formatter = [[NSNumberFormatter alloc] init]; 
[formatter setNumberStyle:NSNumberFormatterCurrencyStyle]; 
[formatter setLenient:YES]; 

NSNumber *number = [formatter numberFromString:@"£23.56"]; 

NSDecimalNumber *minusOne = [NSDecimalNumber decimalNumberWithString:@"-1.00"]; 
NSDecimalNumber *money = [NSDecimalNumber decimalNumberWithDecimal:[number decimalValue]]; 
NSDecimalNumber *negativeMoney = [money decimalNumberByMultiplyingBy:minusOne]; 

NSLog(@"£23.56 is now %@", [negativeMoney description]);