Swift 3 - CoreData - To Many - Inverse Relationship (Tutorial-5)

In the last tutorial we have seen 'To One - Inverse relationship' with a person spouse as an example.

In this tutorial, Let’ see To Many - Inverse relationship.

Please checkout code for this example here

In this example, each person can have a manager (To One) and n number of reportees (To Many) If the person is a manager.

Here, 

Relationship ‘reportees’ 

If Person A is added as a reportee to Person B, as we have given Inverse relationship as manager,

Person B will become the manager for that reportee automatically.

Person A.manager = Person B (Inverse Relationship as manager)

As a person can have multiple reportees If he/she is a manager, reportees is having To Many type relationship with the person.

Relationship ‘manager’ 

If Person A is added as a manager to Person B, as we have given Inverse relationship as reportees,

Person B will become the reportee for that manager automatically.

Person B is now one of the reportees to Person B

As a person can have only one manager, manager is having To One type relationship with the person.

When there is a To Many relationship, Coredata gives it as a NSSet, which is unordered list with no duplicates.

Download the example and see the Person core data class.

     @NSManaged public var manager: Person?

    @NSManaged public var reportees: NSSet?

The beauty of core data is, It gives all accessor methods for adding and removing reportees when we create a Person NSManagedObject subclass.

  extension Person {

    

    @objc(addReporteesObject:)

    @NSManaged public func addToReportees(_ value: Person)

    

    @objc(removeReporteesObject:)

    @NSManaged public func removeFromReportees(_ value: Person)

    

    @objc(addReportees:)

    @NSManaged public func addToReportees(_ values: NSSet)

    

    @objc(removeReportees:)

    @NSManaged public func removeFromReportees(_ values: NSSet)

    

 }

In the example, If the person is a manger, They can select reportees, Where I am using generated accessor method “addToReportees()”

Add Reportee

Reportee Selection

Added Reportee

Manager updated (Inverse Relationship)

Hope this post is useful. Feel free to comment incase of any queries.

Swift 3 - CoreData - To One Relationship (Tutorial-3)

In my earlier CoreData tutorials, We have gone through CRUD operations and validations. 

In this tutorial, Let’s start with Relationships.

I am taking an example where, person will have a address and the relationship of a person with address is To One and it is No Inverse. That means, person knows about the address and address doesn’t know the person.

If we delete person object, address also will get deleted If we set the delete rule as Cascade.

Please check out the code for this example from here  

I have created an Address entity. Person entity holds the relationship as address which of Address(Destination) class. 

There is No Inverse Relation here. That is why address doesn’t know about person. The delete rule here is Cascade. If person is deleted, address will also get deleted.

The type of relationship is To One. Each person will have only one address.

Go through the example link and try to add person with address. Check the sqlite file that core data creates. With our applied relationship and delete rule, If a person is deleted, address will get deleted from database automatically.

In the next tutorial, Let’s see a different relationship type :)

Hope this post is useful. Feel free to comment incase of any queries.