Question

I have a NSString object having multiple conditions specified in it like below:

NSString *strFormula1 = @"\"man\" == \"man\" && 1<5 || 12<9";
NSString *strFormula2 = @"\"[e-mail]\" == \"[e-mail]\" || 9==9 && 8>2 || 2==2";

I want to execute formula specified in the NSString object & find out the answer as BOOL.
Whether the condition specified is returning True or False.

Thanks in advance:)

Answer 1

Just use an NSPredicate like this:

NSString *strFormula1 = @"\"man\" == \"man\" && 1<5 || 12<9";
NSString *strFormula2 = @"\"[e-mail]\" == \"[e-mail]\" || 9==9 && 8>2 || 2==2";
NSString *strFormula3 = @"\"hello\" == \"world\"";

NSPredicate *predicate = [NSPredicate predicateWithFormat:strFormula1];
BOOL result = [predicate evaluateWithObject:nil]; //True

predicate = [NSPredicate predicateWithFormat:strFormula2];
result = [predicate evaluateWithObject:nil]; //True

predicate = [NSPredicate predicateWithFormat:strFormula3];
result = [predicate evaluateWithObject:nil]; //False

And if you’re curious to see how the predicate parsed your expression just use:

NSLog(@"%@", [predicate predicateFormat]);

Which in our case returns:

("man" == "man" AND 1 < 5) OR 12 < 9 //1st Expression
"[e-mail]" == "[e-mail]" OR (9 == 9 AND 8 > 2) OR 2 == 2 //2nd Expression
"hello" == "world" //3rd Expression