浮点数相关精度输出问题

正常输出浮点数

double d = 1234.567890;

NSString *strD1 = [NSString stringWithFormat:@"%f", d];  //结果为@"1234.567890"

    NSString *strD2 = [NSString stringWithFormat:@"%.2f", d];  //保留小数点后两位 结果为1234.57

    NSString *strD3 = [NSString stringWithFormat:@"%0.2f", d];  //保留小数点后两位 结果为1234.57

    short p =8;

    NSString *strP = [NSString stringWithFormat:@"%%.%df",p];

    NSString *strD4 = [NSString stringWithFormat:strP, d];  //动态保留小数点位数 结果为1234.56789000

    NSString *strD5 = [NSNumber numberWithDouble:d].getNoStyleDecimal ; //NSDecimalNumber *dn = [NSDecimalNumber decimalNumberWithString:self.stringValue]; return dn.stringValue;  结果为1234.56789

当d=0.000000001时，结果如下