NSFetchedResultsController: unnamed section

Question

Created Feb ’20

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When working with a table view controller, an unnamed section is generated by the NSFetchedResultsController for those items in my CoreData model that lack a certain relationship ('belongsToCategory').

In fact, this is almost exactly the behavior I want - I would rather use a special name instead of an empty one, but I can easily rename the empty section name on the fly in tableView(_:titleForHeaderInSection:).

But how do I get rid of the error message in the log in the first place?

CoreData: error: (NSFetchedResultsController) A section returned nil value for section name key path 'belongsToCategory.name'. Objects will be placed in unnamed section

Can I override some method or anything in order to return a default name if the relationship is not set?

Answered by LPG in 407921022

Found the solution myself:

extension Product {
    @objc var computedName:String { // @objc is crucial for making it KVC compliant!
        get {
            if belongsToCategory != nil {
                return belongsToCategory!.name!
            } else {
                return "special"
            }
        }
    }
}

In the NSFetchedResultsController use "computedName" for section name key path instead of "belongsToCategory.name".

Data model here is: entity "Product" <<-- "belongsToCategory" ---> entity "Category". Both entities have name attributes.

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Answer 1

LPG OP

Feb ’20

Accepted Answer

Found the solution myself:

extension Product {
    @objc var computedName:String { // @objc is crucial for making it KVC compliant!
        get {
            if belongsToCategory != nil {
                return belongsToCategory!.name!
            } else {
                return "special"
            }
        }
    }
}

In the NSFetchedResultsController use "computedName" for section name key path instead of "belongsToCategory.name".

Data model here is: entity "Product" <<-- "belongsToCategory" ---> entity "Category". Both entities have name attributes.

0