NSNumberFormatter numberFromString问题

Question

我需要从UITextfield获取一个字符串，并将其格式化如下：

4.99999 -> 4.999
4.12    -> 4.12
.89     -> 0.89

NSNumberFormatter *numberFormatter = [[NSNumberFormatter alloc] init];
[numberFormatter setNumberStyle:NSNumberFormatterDecimalStyle];
[numberFormatter setMaximumFractionDigits:3];
[numberFormatter setPositiveFormat:@"##0.###"];

DLog(@"formatted number %@",[numberFormatter numberFromString:string]);

问题是，当我在textfield中键入0.999978并且格式化的数字是0.999978 (这是不正确的)时，它应该是0.999

Answer 1

试试看：

NSNumber  *aNum = [NSNumber numberWithDouble:[string doubleValue]];
NSNumberFormatter *numberFormatter = [[NSNumberFormatter alloc] init];
[numberFormatter setNumberStyle:NSNumberFormatterDecimalStyle];
[numberFormatter setPositiveFormat:@"##0.###"];
[numberFormatter setRoundingMode:NSNumberFormatterRoundFloor];

DLog(@"formatted string %@",[numberFormatter stringFromNumber:aNum]);