Question

This is a sample of an array I would like to get value from it.

coursesArray = [[NSMutableArray alloc]init];

// AR111:
[coursesArray addObject:[[NSMutableDictionary alloc] initWithObjectsAndKeys:
                           @"MUR",@"courseType",  
                           @"AR111",@"courseCode",
                           @"Arabic Communication Skills (I)",@"courseName",
                           @"3",@"creditHours",
                           @"",@"preRequisites",
                           @"63.000",@"coursePrice",
                           @"6.000",@"courseEPP",
                           @"This course aims at .",@"courseDetails",
                           nil]];

And this is my code to get the value to it.

NSManagedObjectContext *context = [self.fetchedResultsController managedObjectContext];
NSEntityDescription *entity = [[self.fetchedResultsController fetchRequest] entity];

int i = 0;
for (i = 0; i < [coursesArray count] ; i++) {

NSManagedObject *newManagedObject = [NSEntityDescription insertNewObjectForEntityForName:[entity name] inManagedObjectContext:context];

    [newManagedObject setValue:[[coursesArray objectAtIndex: i ]forKey:@"courseName"] forKey:@"courseName"];
}

If any one can help me to correct the following part:

[newManagedObject setValue:[[coursesArray objectAtIndex: i ]forKey:@"courseName"] forKey:@"courseName"];

The values will be add in to core data forKey:@”courseName”.

Answer 1

[newManagedObject setValue:[[coursesArray objectAtIndex: i ]forKey:@"courseName"] forKey:@"courseName"];

This is a classic case of putting too much code on one line, I think. I don’t expect this actually compiles?

Let’s try and break it down into sections. I’ve taken the central bit of code out and replaced it with XX:

[newManagedObject setValue:XX forKey:@"courseName"];

This bit looks fine. setValue:forKey is a valid method for a managed object.

XX is:

[YY forKey:@"courseName"]

It’s not clear if this is right or not, but it doesn’t look good – the method name doesn’t seem right.

YY is:

[coursesArray objectAtIndex:i]

This is fine, and it returns a mutable dictionary. But dictionaries don’t implement a method called forKey:. They do implement a method called objectForKey:, though, which is what you want.

So, your corrected line should be:

[newManagedObject setValue:[[coursesArray objectAtIndex:i] objectForKey:@"courseName"] forKey:@"courseName"];

If you’re writing a lot of code like this, custom objects with properties to hold data members suddenly make a lot more sense. The forKey: all over the place soon becomes unreadable.