双精度损失

Question

I m storing some values into the sqlite database. So the data is collected from a textfield as a string and then converted to double and persisted.

This is something which I tried

NSDecimalNumber answer;
value.answer = [NSDecimalNumber decimalNumberWithString:answerValue];

If you use 6532.002 as the data, it loses its precision.

Any idea how to solve this issue. I understand that similar issue has been posted numerous times but after trying a number of recommended solutions I have not been able to solve the issue yet.

Thanks

Answer 1

Your number can't be represented exactly as a double precision floating point value due to the way floating point numbers work. You'll need to find another way to represent it if you need that sort of precision. Some options are to use an arbitrary precision library (such as the ones listed in this Wikipedia entry ), or to use a fixed point representation with the number of bits you need to obtain the precision you need. If you're only displaying the numbers, then you should keep it as a string.

Answer 2

采用

float value=[textField.text floatValue];