-(NSString *)notRounding:(float)price afterPoint:(int)position{
    NSDecimalNumberHandler* roundingBehavior = [NSDecimalNumberHandler decimalNumberHandlerWithRoundingMode:NSRoundDown scale:position raiseOnExactness:NO raiseOnOverflow:NO raiseOnUnderflow:NO raiseOnDivideByZero:NO];
    NSDecimalNumber *ouncesDecimal;
    NSDecimalNumber *roundedOunces;
    
    ouncesDecimal = [[NSDecimalNumber alloc] initWithFloat:price];
    roundedOunces = [ouncesDecimal decimalNumberByRoundingAccordingToBehavior:roundingBehavior];
    [ouncesDecimal release];
    return [NSString stringWithFormat:@"%@",roundedOunces];
}

介紹一下參數(shù)：
price:需要處理的數(shù)字，
position：保留小數(shù)點(diǎn)第幾位，
然后調(diào)用

float s =0.126;
NSString *sb = [self notRounding:s afterPoint:2];
NSLog(@"sb = %@",sb);

輸出結(jié)果為：sb = 0.12

接下來(lái)介紹NSDecimalNumberHandler初始化時(shí)的關(guān)鍵參數(shù)：decimalNumberHandlerWithRoundingMode：NSRoundDown，
NSRoundDown代表的就是 只舍不入。
scale的參數(shù)position代表保留小數(shù)點(diǎn)后幾位。