Question

Is it possible to do arithmetics using Obj-C Key-Value Coding? I am looking for something like this:

[obj valueForKeyPath:@"(val1+val2)"]

or do you have to implement a property that adds the two values manually?

Answer 1

Arithmetic using KVC is not possible.

You can do arithmetic with strings and then pass it to [obj valueforKeyPath:...] as :

NSString *val1=@"3";
NSString *val2=@"5";

NSString *formula = [NSString stringWithFormat:@"%@+%@",val1,val2];

NSExpression *exp = [NSExpression expressionWithFormat:formula];
NSNumber *resultForCustomFormula = [exp expressionValueWithObject:nil context:nil];

NSLog(@"%f", [resultForCustomFormula floatValue]);