Question

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I am trying to use NSPredicate in Swift to query Core Data but it throws an EXC_BAD_ACCESS(Code=1, address=0x1) error when trying to run it, what am I doing wrong?

Here is the file where the error happens

class LevelsScreenModel : UIViewController {

func getWord(level: Int, section: Int) -> String
{
    let fetchRequest = NSFetchRequest(entityName: "Words")

    //This is the line where the error happens
    fetchRequest.predicate = NSPredicate(format: "level = %@", level)
    fetchRequest.predicate = NSPredicate(format: "section = %@", section)

    let word = AppDelegate().managedObjectContext!.executeFetchRequest(fetchRequest, error: nil) as [Words]

    if(word.count > 1)
    {
        for words in word
        {
            println(words.word)
            return words.word
        }
    }

    return "ERROR"
  }
}

Автор: Cesarg219 Источник Размещён: 20.02.2015 02:37

Answer 1

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Решение

The %@ placeholder in predicate format strings is for Objective-C objects, so you have to wrap the integer into an NSNumber:

fetchRequest.predicate = NSPredicate(format: "level = %@", NSNumber(integer: level))

or use ld instead to format a (long) integer:

fetchRequest.predicate = NSPredicate(format: "level = %ld", level)

Note also that

fetchRequest.predicate = NSPredicate(format: ...)
fetchRequest.predicate = NSPredicate(format: ...)

does not create a compound predicate, the seconds assignment simply overwrites the first. You can use an NSCompoundPredicate:

let p1 = NSPredicate(format: "level = %ld", level)!
let p2 = NSPredicate(format: "section = %ld", section)!
fetchRequest.predicate = NSCompoundPredicate.andPredicateWithSubpredicates([p1, p2])

or simply combine the predicates with "AND":

fetchRequest.predicate = NSPredicate(format: "level = %ld AND section = %ld", level, section)

Автор: Martin R Размещён: 20.02.2015 06:01

Answer 2

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3337 Репутация автора

Instead of fussing around with format conversions and AND subpredicates, you could use the PredicatePal framework:

fetchRequest.predicate = *(Key("level") == level && Key("section") == section)

Note that you'll need to use == instead of = for equality comparison.

Автор: Glen Low Размещён: 28.12.2015 05:37

Swift NSPredicate throwing EXC_BAD_ACCESS(Code=1, address=0x1) when compounding statements

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