Catch an exception for invalid user input in swift

Question

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/kon

Answer 1

More "Swifty" solution:

@implementation TryCatch

+ (BOOL)tryBlock:(void(^)())tryBlock
           error:(NSError **)error
{
    @try {
        tryBlock ? tryBlock() : nil;
    }
    @catch (NSException *exception) {
        if (error) {
            *error = [NSError errorWithDomain:@"com.something"
                                         code:42
                                     userInfo:@{NSLocalizedDescriptionKey: exception.name}];
        }
        return NO;
    }
    return YES;
}

@end

This will generate Swift code:

class func tryBlock((() -> Void)!) throws

And you can use it with try:

do {
    try TryCatch.tryBlock {
        let expr = NSExpression(format: "60****2")
        ...
    }
} catch {
    // Handle error here
}