12_Objective-C Error Handling

Error handling is provided with NSError class available in Foundation framework.

An NSError object encapsulates richer and more extensible error information than is possible using only an error code or error string.

The core attributes of an NSError object are an error domain (represented by a string), a domain-specific error code and a user info dictionary containing application specific information.

NSError Object consists of:

  • Domain: The error domain can be one of the predefined NSError domains or an arbitrary string describing a custom domain and domain must not be nil.
  • Code: The error code for the error
  • User Info: The userInfo dictionary for the error and userInfo may be nil.

create a custom error

NSString *domain = @"com.MyCompany.MyApplication.ErrorDomain";
NSString *desc = NSLocalizedString(@"Unable to complete the process", @"");
NSDictionary *userInfo = @{ NSLocalizedDescriptionKey : desc };
NSError *error = [NSError errorWithDomain:domain code:-101 userInfo:userInfo];

Here is complete code of the above error sample passed as reference to an pointer

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