CODEWITHSUNDEEP
ioscore-dataswift3
Antonio K
Antonio K

Reputation: 154

'NSInvalidArgumentException', reason: 'to-many key not allowed here'

I saw already some approaches but nothing which would solve my problem.

I create two entities, Shop and Article. Shop has the relationship "articles" and Article "shop", both are many to many and ordered relationships.

enter image description here

For the shop I have one CollectionViewController and for Articles TableViewController. After selecting one Shop I send it via segue to the ArticleTableViewController, where I can add Articles to the current shop.

ArticleTableViewController

var articles: [Article] = []
var currentShop: Shop?

@IBAction func pressAddButton(_ sender: UIButton) {
    let article = Article(context: managedContext!)
    article.name = "Milk"

    currentShop?.addToArticles(article)

    saveManagedContext()
    tableView.reloadData()
}

 func loadArticles () {

    let articleFetchRequest: NSFetchRequest<Article> = Article.fetchRequest()
    articleFetchRequest.predicate = NSPredicate(format: "shop = %@", currentShop!)

    do {
        articles = try managedContext.fetch(articleFetchRequest)

    } catch let error as NSError {
        print("Could not fetch \(error), \(error.userInfo)")
    }
}

func saveManagedContext() {
    do {
        try managedContext?.save()
    } catch let error as NSError {
        print("Could not save \(error), \(error.userInfo)")
    }
}

If I build and run and select one shop, the app terminated with the reason: 'NSInvalidArgumentException', reason: 'to-many key not allowed here'

I think the problem is the predicate, because if I comment it out and run again and then select the shop it works fine, but all shops have the same articles that I added.

How to fetch just the articles for the selected Shop?

Upvotes: 2

Views: 1548

Answers (1)

Dave Weston
Dave Weston

Reputation: 6635

Try 

 NSPredicate(format: "ANY shop = %@", currentShop!)

Or, alternatively, can you just use currentShop.articles? That will return a Set, which may not suit your purpose in this case, but... generally you can just follow relationships.

Upvotes: 6

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