有没有办法防止stringWithFormat四舍五入？

NSNumberFormatter *formatter = [[NSNumberFormatter alloc] init];
[formatter setNumberStyle:NSNumberFormatterDecimalStyle];
[formatter setRoundingMode:NSNumberFormatterRoundDown];
[formatter setMaximumFractionDigits:2];

NSNumber *number = [NSNumber numberWithFloat:3.14159];
NSString *formattedString = [formatter stringFromNumber:number];

NSLog(@"Formatted string: %@", formattedString);

Formatted string: 3.14