can I convert + as an NSString to addition operator directly?

Question

I have a mathematical equation in string format.

Is there a way to convert @"+"(String constant) directly to addition operator in objective C Or

I have to use If-Else statements to solve this equation ??

What's the particular use case that you're inquiring about this for? Ie why do you want to do this? — Alfie Hanssen, Jul 29 '13 at 17:16
123+456+678-985 it is in the form of a string constant. can I convert it into mathematical equation like (float I=123+456+678-985) — DemonicPossessions1991, Jul 29 '13 at 17:21
If it's just @"+" just compare strings. If you actually want to evaluate expressions, then I suggest look for an open source implementation of string equations. — 0xSina, Jul 29 '13 at 17:22
yes, of course. comparing with IF-ELSE work fine, but I wasn't worried about that. I just wanted to know if there is a way to convert this directly..:) — DemonicPossessions1991, Jul 29 '13 at 17:26

score 3 · Accepted Answer · answered Jul 29 '13 at 17:26

3

NSPredicate * parsed = [NSPredicate predicateWithFormat:@"123+456+678-985 = 0"];
NSExpression * left = [(NSComparisonPredicate *)parsed leftExpression];
NSNumber * result = [left expressionValueWithObject:nil context:nil];
float i = [result floatValue];

answered Jul 29 '13 at 17:26

0xSina

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You don't need the predicate, compare http://stackoverflow.com/questions/12500232/i-have-formula-in-a-nsstring-how-to-evaluate-it/12500518#12500518. – Martin R Jul 29 '13 at 17:38

score 0 · Answer 2 · answered Jul 29 '13 at 17:19

0

if([yourString isEqualToString:@"+"])
{
     //Do something

}

This code should work.

answered Jul 29 '13 at 17:19

Abdullah Shafique

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yes, of course. this work fine but I wasn't worried about that just wanted to know if there is a way to convert is directly..:) – DemonicPossessions1991 Jul 29 '13 at 17:23
Remember the check :) – Abdullah Shafique Jul 29 '13 at 17:24

score 0 · Answer 3 · answered Dec 02 '14 at 10:23

You can use NSExpression to achieve this

NSString *expressionFormat = [NSString stringWithFormat:@"(%d %@ %d)",firstNumber,arcthimaticOperator,secondNumber];
NSExpression *expression = [NSExpression expressionWithFormat:expressionFormat];
NSNumber *result = [expression expressionValueWithObject:nil context:nil];
NSLog(@"%@", result);

Please make sure you enter the correct format else the above code will throw exception.

can I convert + as an NSString to addition operator directly?

3 Answers3