NSNumberFormatter numberFromString問題

Question

我需要從UITextfield中獲取一個字符串並將其格式化為以下格式：

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]);

問題是，當我在文本字段中鍵入0.999978且格式化的數字為0.999978（不正確）時，它應該為0.999

Answer 1

試試看：

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]);