Save User using Realm Object

Question

I am creating a project. I want if the userID already exist, it doesn't add the user. But somehow my code isn't working properly.

This is my Realm Model Object (User.swift):

import Foundation
import RealmSwift

class User: Object {

    @objc dynamic var userID = Int()
    @objc dynamic var username = ""
    @objc dynamic var full_name = ""
    @objc dynamic var myBool = Bool()

    override static func primaryKey() -> String? {
        return "userID"
    }
}

And this is the button to add users:

@IBAction func add(_ sender: Any) {
        let myUser = User()
        let JSON_userID = Int(arc4random_uniform(5)) // This is temporary. I am going to get code from JSON, but using random for testing purpose.

        if (myUser.userID != JSON_userID) {
            myUser.userID = JSON_userID
            myUser.username = "myUsername"
            myUser.full_name = "My Name"

            let realm = try! Realm()
            try! realm.write {
                realm.add(myUser)
            }
        }
        else {
            print("Already exist")
        }
    }

Sometimes it runs the code, but most of the times it crashes with error:

libc++abi.dylib: terminating with uncaught exception of type NSException.

You have to query DB and test against all the users in it. Your if statement will be always true because you always test with newly created User. — kirander

Sparga Sparga · Accepted Answer · 2017-10-02T22:23:04

As you defined a primary key in your User object, Realm can handle this automatically if you set the update parameter to true inside the write closure.

let realm = try! Realm()
try! realm.write {
   realm.add(myUser, update: true)
}

If the update parameter is not set or false, Realm will throw an exception when you try to add an object with an existing primary key.

This makes the if / else condition useless. It can be removed.

If you need to know if the user already exists, you can request the Realm with the primary key value:

realm.object(ofType: User.self, forPrimaryKey: JSON_userID)

The result will be nil if the user does not exist.

Save User using Realm Object

1 Answers