如何从floatValue获取具有与float值相同的精度数的NSDecimalNumber？

Question

I logged two NSDecimalNumber

NSLog(@"%@",[[NSDecimalNumber alloc] initWithFloat:2.675f]);
NSLog(@"%@",[[NSDecimalNumber alloc] initWithFloat:2.000f]);

I got the results in the console as

10:26 2013-05-16 10:23:20.807 SampleTest[1097:19d03] 2.674999952316284416
2013-05-16 10:23:22.484 SampleTest[1097:19d03] 2

My expected result is 2.0000 . It is fine to have any number of zero's after decimal But should have atleast one zero after the decimal point. It will be hard for me to change the NSDecimalNumber datatype.

How can I acheive that. Can anyone help me out. Thanks in advance.

Answer 1

As decimal number is a represented in base-10 arithmetic. An instance can represent any number that can be expressed as mantissa x 10^exponent where mantissa is a decimal integer

Therefore 0s after decimal gets truncated. If you want explicitly then you need to use float or double .

NSDecimalNumber *deciA=[NSDecimalNumber decimalNumberWithMantissa:2675 exponent:-3 isNegative:NO]; 
NSDecimalNumber *deciB=[NSDecimalNumber decimalNumberWithMantissa:2000 exponent:-3 isNegative:NO];

    NSLog(@"deciA is %@",deciA);
    NSLog(@"deciB is %@",deciB);

Output:

deciA is 2.675

desiB is 2

You can do this way:

NSDecimalNumber *deciA=[[NSDecimalNumber alloc] initWithFloat:2.675f];
NSDecimalNumber *deciB=[[NSDecimalNumber alloc] initWithFloat:2.000f];
NSLog(@"deciA is %.3lf",[deciA doubleValue]);
NSLog(@"deciB is %.3lf",[deciB doubleValue]);

Output:

deciA is 2.675

desiB is 2.000