I'm trying to do math from a string. When I turn a string into a math problem with NSExpression, and then get the result with expressionValue, Swift assumes I want an Integer. Consider these two P...

I want to calculate a string, which I'm doing by this: NSExpression *expression = [NSExpression expressionWithFormat:calculationString]; float result = [[expression expressionValueWithObject:nil c...

I'm trying to write a SUBQUERY for an NSPredicate. My problem is I don't have the query on hand for the predicate portion of the SUBQUERY. Is there a way to nest an NSPredicate inside the SUBQUERY?...

Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'Unable to parse the format string "12+6+ == 1"' I want to validate expression is valid or not. And I am trying...

I have a predicate editor, which the template was generate via the following: NSArray * test = [NSArray arrayWithObjects: [NSExpression expressionForKeyPath: @"Abc"], [NSExpression expressionFo...

I want to validate user created expressions (like "2+2", "5+7" or more complex). I use NSExpression class to parse and calculate this expressions. This is my Playground code: import UIKit l...

For reference, the problem I'm trying to solve is efficiently finding and removing duplicates in a table that could have a lot of entries. The table I am working with is called PersistedDay with a...

I am trying this code that is a calculator. How can I handle input from the user that is not valid? //ANSWER: Bridging header to Objective-C// https://github.com/kongtomorrow/TryCatchFinally-Swift...

I have already implemented a custom calculator where I am using following code to evaluate the arithmetic expression something like 5+3*5-3. - (NSNumber *)evaluateArithmeticStringExpression:(NSStr...

In my code I am evaluating strings as mathematical expressions for example: NSString *formula=@"9*7"; NSExpression *expr =[NSExpression expressionWithFormat:formula]; NSLog(@"%@", [[expr expressio...

I'm new in Core Data, so i want to write simple fetch request to group result by some field and also a count of another field in that group. so for example i have products table i want to retrieve ...