Swift Question
Ambiguous use of 'fetch' error
I am using SWIFT 3.0 on Xcode 8.0
I am trying to loop through the fetched results that was created through template.
let request = model.fetchRequestTemplate(forName: "template")
do {
let result = try context.fetch(request!) // Error on this line
for item: EntityClassName in result! {
...
}
} catch {
...
}
I get the error "Ambiguous use of 'fetch'". Is my approach wrong? If so what is the right way to loop through the fetched results?
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Answer Source
The method fetch you are using returns [Any], because it could be [Dictionary] or [NSManagedObject] or one of its subclasses.
You have to cast [Any] to the proper type
let result = try context.fetch(request!) as! [EntityClassName]
for item in result {
...
}
The forced unwrapping is absolutely safe because according to the fetch request it returns always [EntityClassName].
Swift 3 reveals a lot of mistakes made but tolerated in Swift 2 to improve the type safety.
Alternatively you could use the new API with generics, this avoids some type casting.
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