NSString category calculator

Question

I'm trying to find a way to calculate result from NSString. Is there a simple NSString calculator category?

NSString *str = @"10+20/2";
int result = [[str stringByCalculatingResult] intValue];
NSLog (@"result:%i", result);

Prefer output:

result:20

Thank you for solution.

Category:

//NSString+Calculator.h
@interface NSString (Calculator)
- (NSString*)stringByCalculatingResult;
@end

//NSString+Calculator.m
@implementation NSString (Calculator)
- (NSString*)stringByCalculatingResult
{
    NSExpression *expression = [NSExpression expressionWithFormat:self];
    NSNumber *value = [expression expressionValueWithObject:nil context:nil];
    return [value stringValue];
}
@end

what about using NSPredicate like this? http://stackoverflow.com/questions/8618005/how-to-convert-string-to-math-equation-in-objective-c — Alberto Vitale, Jul 30 '13 at 13:47
possible duplicate of [How to evaluate the string equation in ios](http://stackoverflow.com/questions/16785873/how-to-evaluate-the-string-equation-in-ios) — Martin R, Jul 30 '13 at 13:49
possible duplicate of [Objective-C Calculating string value](http://stackoverflow.com/questions/6072439/objective-c-calculating-string-value) — Daniel, Jul 30 '13 at 13:50

score 2 · Accepted Answer · answered Jul 30 '13 at 13:42

2

You should look at using the NSExpression class which can evaluate mathematical expressions for you:

NSExpression *expression = [NSExpression expressionWithFormat:@"10 + 20 / 2"];
id value = [expression expressionValueWithObject:nil context:nil];

answered Jul 30 '13 at 13:42

Wain

118,658
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score 0 · Answer 2 · answered Jul 30 '13 at 13:44

0

You can take a look at this mathematical parser library

answered Jul 30 '13 at 13:44

zahreelay

1,742
12
18

NSString category calculator

2 Answers2