有什么办法可以给Objective-C中的算术计算提供格式？

Question

i want to define something similar to a computation method:

NSString *format = @"%d + 1";

In my code i want to do something like:

int computedNumber = sum(format,5) => the result should be 6.

could you give some suggestions? thank you

EDIT: or something similar to: NSNumber *no = [NSNumber numberWithFormat:format,5];

Answer 1

It is not normally possible, however there have been written parsers for this specific tasks, to mention DDMathParser by SO user Dave DeLong .

But for what task do you really need this? You have the + operator, and then you perform the sum function? Couldn't you simply parse the number at the end of the format, then perform the operation you'd like?

Answer 2

Using Macro can be an alternative solution to your problem. You can define a macro like the following,

#define INC(a) (a + 1)

Here, INC and a are user-defined. You can give them any name you want. Compiler will substitute (a + 1) in your code, where ever you call INC(a) . For example, consider the following,

int computedNumber = INC(5);

After the compilation the code will be,

int computedNumber = (5 + 1); // the result during the execution is 6.