Examples of Error Handling in Objective-C ❤

In Objective-C the main method used to handle the errors is NSError let’s see some examples to understand how this method works.

Example 1:

Let’s see the example where the NSError method is used to find out the error in the program, if there is no error in the program then we get the exact output that we want but if there is any error in the program then the NSError method comes into play.

ObjectiveC

#import <Foundation/Foundation.h>
 
// Function that may produce an error
BOOL performTaskWithError(NSError **error) {
    // Simulate an error condition
    if (error != NULL) {
        NSDictionary *userInfo = @{
            NSLocalizedDescriptionKey: @"Task failed",
            NSLocalizedFailureReasonErrorKey: @"The task encountered an error",
        };
        *error = [NSError errorWithDomain:@"com.example.error" code:1 userInfo:userInfo];
        return NO;
    }
 
    // Simulate successful task execution
    return YES;
}
 
int main(int argc, const char * argv[]) {
    @autoreleasepool {
        NSError *error = nil;
 
        if (!performTaskWithError(&error)) {
            NSLog(@"Error: %@", error.localizedDescription);
            NSLog(@"Failure Reason: %@", error.localizedFailureReason);
        } else {
            NSLog(@"Task completed successfully");
        }
    }
    return 0;
}

Output:

Output

Explanation:

In this program, there are some programming errors so by the help of the NSError method we get the error in the result that the Task failed due to an error. if there is no error then the desired output will be printed.

Example 2:

In this example, we are using the NSError method in the calculator program and when there is any condition like divide by zero then the NSError method throws that error.

ObjectiveC

#import <Foundation/Foundation.h>
 
@interface Calculator : NSObject
 
- (NSInteger)divide:(NSInteger)numerator by:(NSInteger)denominator error:(NSError **)error;
 
@end
 
@implementation Calculator
 
- (NSInteger)divide:(NSInteger)numerator by:(NSInteger)denominator error:(NSError **)error {
    if (denominator == 0) {
        if (error != NULL) {
            NSString *domain = @"CalculatorErrorDomain";
            NSInteger code = 1;
            NSDictionary *userInfo = @{NSLocalizedDescriptionKey: @"Cannot divide by zero."};
            *error = [NSError errorWithDomain:domain code:code userInfo:userInfo];
        }
        return 0;
    }
    return numerator / denominator;
}
@end
 
int main(int argc, const char * argv[]) {
    @autoreleasepool {
        Calculator *calculator = [[Calculator alloc] init];
         
        NSError *error = nil;
        NSInteger result = [calculator divide:10 by:0 error:&error];
         
        if (error) {
            NSLog(@"Error: %@", error.localizedDescription);
        } else {
            NSLog(@"Result: %ld", (long)result);
        }
    }
    return 0;
}

Output:

Output

Explanation:

So here the error in the program is like in a calculator if we are dividing any natural number by zero then we get the error. In this program, this is the error and by the help of the error handling method we can find the error and the lines where the error is by the help of this technique, it is straightforward for the user to identify the error and create a robust code.

Example 3:

In the below Objective-C program, BNSException is implemented.

ObjectiveC

#import <Foundation/Foundation.h>
 
// Function that may throw an exception
void performTaskWithException(void) {
    // Simulate an exception
    @throw [NSException exceptionWithName:@"TaskFailureException" reason:@"The task encountered an exception" userInfo:nil];
}
 
int main(int argc, const char * argv[]) {
    @autoreleasepool {
        @try {
            performTaskWithException();
            NSLog(@"Task completed successfully");
        } @catch (NSException *exception) {
            NSLog(@"Exception: %@", exception.reason);
        }
    }
    return 0;
}

Output:

Exception: The task encountered an exception

Output

With the help of this method also we can find the errors in the program of Objective-C.

Example 4:

Below Objective-C program demonstrates combining NSError and NSException.

ObjectiveC

#import <Foundation/Foundation.h>
 
// Function that may produce an error or throw an exception
BOOL performTaskWithErrorAndException(NSError **error) {
    // Simulate an error condition
    if (error != NULL) {
        NSDictionary *userInfo = @{
            NSLocalizedDescriptionKey: @"Task failed",
            NSLocalizedFailureReasonErrorKey: @"The task encountered an error",
        };
        *error = [NSError errorWithDomain:@"com.example.error" code:1 userInfo:userInfo];
        return NO;
    }
 
    // Simulate an exception
    @throw [NSException exceptionWithName:@"TaskFailureException" reason:@"The task encountered an exception" userInfo:nil];
}
 
int main(int argc, const char * argv[]) {
    @autoreleasepool {
        NSError *error = nil;
 
        @try {
            if (!performTaskWithErrorAndException(&error)) {
                NSLog(@"Error: %@", error.localizedDescription);
                NSLog(@"Failure Reason: %@", error.localizedFailureReason);
            } else {
                NSLog(@"Task completed successfully");
            }
        } @catch (NSException *exception) {
            NSLog(@"Exception: %@", exception.reason);
        }
    }
    return 0;
}

In this example, we have used both the classes NSError and NSException in the program to find the errors in the code.

Output:

Output

Examples of Error Handling in Objective-C

Example 1:

ObjectiveC

Example 2:

ObjectiveC

Example 3:

ObjectiveC

Example 4:

ObjectiveC

Error Handling in Objective-C

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