gistfile1.txt

Note: clientId and facId are primary keys to the server database, numbers stored in NSStrings

// Mandatory fields: clientId, facId
- (NSError *)validateData {
    
    id sel1 = [NSValue valueWithPointer:@selector(clientId)];
    id sel2 = [NSValue valueWithPointer:@selector(facId)];
    
    return [self validateMandatoryFields:@[sel1, sel2]];
}
- (NSError *)validateMandatoryFields:(NSArray *)fields {

    
    NSMutableArray *nilFields = [NSMutableArray array];

    for (id field in fields) {

        
        SEL selector = [field pointerValue];

        
        NSMethodSignature *method = [self methodSignatureForSelector:selector];

        NSInvocation *invocation = [NSInvocation invocationWithMethodSignature:method];

        [invocation setSelector:selector];

        [invocation invokeWithTarget:self];



        // We must use __unsafe_unretained to avoid decreasing retain count

        id __unsafe_unretained value;

        [invocation getReturnValue:&value];

        
        if (!value) {

            [nilFields addObject:NSStringFromSelector(selector)];

        }

    }



    if (nilFields.lastObject) {

        NSString *missingFields = [nilFields componentsJoinedByString:@", "];

        
        NSMutableDictionary *userInfo = [NSMutableDictionary dictionary];

        userInfo[NSLocalizedFailureReasonErrorKey] = NSLocalizedString(@"Invalid Server Response", nil);

        userInfo[NSLocalizedDescriptionKey] = NSLocalizedString(@"Please contact administrator and/or try again later.", nil);

        
        PPLogError(kPELCAPIGlobal, @"VALIDATION ERROR: Model: %@, Fields: %@", NSStringFromClass([self class]), missingFields);

        return [[NSError alloc] initWithDomain:kPPErrorDomainApp code:PPAppErrorInvalidData userInfo:userInfo];

    } else {

        return nil;

    }

}