Question

The code below shows the way I am preparing the params to be submitted to the server. I have a if-else clause to check and determine what params to submit i.e. if question id exists, submit only question id, else submit question text and topic id.

However, I feel that this is a little repetitive and not the best form of coding (in my POV). How can I refactor the code to make it more efficient (remove duplicate)

if(self.question._id || [self.question._id isEqual:[NSNull null]])
{
    //Set up params for submission
    NSDictionary *params= [[NSDictionary alloc] initWithObjectsAndKeys:
                          self.answer.text, @"text",
                          //if question id exists, submit question id only 
                          self.question._id, @"question_id", 
                          shareFb, @"fbShare", 
                          shareTwitter, @"twitterShare",
                          self.question.source,@"questionSource",
                          self.answer.videoId,@"youtube_id",
                          nil
                          ];
}
else
{
    //Set up params for submission
    NSDictionary *params= [[NSDictionary alloc] initWithObjectsAndKeys:
                          self.answer.text, @"text", 
                          //else submit question text and topic id
                          self.question.text, @"question_text",
                          self.question.topic._id, @"topic_id", 
                          shareFb, @"fbShare", 
                          shareTwitter, @"twitterShare",
                          self.question.source,@"questionSource",
                          self.answer.videoId,@"youtube_id",
                          nil
                          ];

Answer 1

Use a mutable dictionary, then you can add in the extra fields

NSMutableDictionary *params= [[NSMutableDictionary alloc] initWithObjectsAndKeys:
        self.answer.text, @"text",
        //if question id exists, submit question id only 
        self.question._id, @"question_id", 
        shareFb, @"fbShare", 
        shareTwitter, @"twitterShare",
        self.question.source,@"questionSource",
        self.answer.videoId,@"youtube_id",
        nil
        ];

if(!(self.question._id == nil || [self.question._id isEqual:[NSNull null]]))
{
    [params setObject:self.question.text forKey:@"question_text"];
    [params setObject:self.question.topic._id forKey:@"topic_id"];
}

EDIT IN RESPONSE TO COMMENT 1

If any of the params being set in the first statement above might be nil, you will need to be more careful

NSMutableDictionary *params= [[NSMutableDictionary alloc] init];
if (self.answer.text) {
    [params setObject:self.answer.text forKey:@"text"];
}
•
•  // all the params between self.answer.text and self.answer.videoId
•
if (self.answer.videoId) {
    [params setObject:self.answer.videoId forKey:@"youtube_id"];
}
if(!(self.question._id == nil || [self.question._id isEqual:[NSNull null]]))
    {
        if(self.question.text) {
            [params setObject:self.question.text forKey:@"question_text"];
        }
        if (self.question.topic._id) {
            [params setObject:self.question.topic._id forKey:@"topic_id"];
        }
    }
}

You cannot set nil object to key (ie [params setObject:nil forKey:@"key] will crash)