从CloudKit Swift获取独特的价值

Question

I have a database students with columns : courseID, StudentID,FirstName, LastName

Now a student can take more than one course.

I have a screen where I am fetching just the students names. And so obviously I am getting duplicate values. Now I know I can change the type of courseID from string to a string list to do away this problem but that would mean a hell lot of coding changes. is there anyway I can modify my CKQuery to fetch distinct values?

As of now the code looks like this:

func FetchRecords(){
        print("Fetch Records")
        let predicate = NSPredicate(value: true)
        let query = CKQuery(recordType: "Students", predicate: predicate)
        let operation = CKQueryOperation(query: query)
        operation.desiredKeys = ["FirstName","LastName","StudentID"]

        var newStud = [Student]()
        print("Begin")
        operation.recordFetchedBlock = { (record)  in
            let stud_rec = Student()
            print(record["FirstName"] as! String)
            stud_rec.FName = (record["FirstName"] as! String)
            stud_rec.LName = (record["LastName"] as! String)
            stud_rec.MatrN = (record["StudentID"] as! String)
            newStud.append(stud_rec)
        }

Answer 1

Amrita I think there is data model design issue where you have felt one of consequences -- a lot of "duplicate values".

The root solution is to avoid many-many relationship between courseID and studentID via a record type say Enrollment to track which student takes which course at which year. This of course demands a "hell lot of coding change." that you also want to avoid.

So maybe you may try this quick surface patch to "fetch distinct values" where you may use Swift Set operations to deal with fetched duplicates as below:

let fetchedDuplicate = ["Jon", "Sid", "Tom", "Jon"]
let uniqueSet = Set(fetchedDuplicate) // it is now {"Jon", "Sid", "Tom"}
let uniqueArray = Array(uniqueSet) // ["Jon", "Sid", "Tom"]

I hope it helps.