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.

Objective C NSPredicate Part 4/4

In my earlier posts on NSPredicate, We have discussed,

Basic Comparisons,

String Comparisons,

Compound Comparisons.

In this part, let's see some Relational operations along with compound predicates.

• IN    
• ALL
• ANY
• SOME
• NONE

We have already covered IN operation in Part 3/4. To discuss remaining Relational operations, let's take another data set.

Let's say fetching all the departments in an organization given the below JSON response.

[

  {

    "name" : "Banking",

    "employees" : [

      {

        "name" : "Tim",

        "salary" : 45000

      },

      {

        "name" : "Smith",

        "salary" : 19000

      },

      {

        "name" : "George",

        "salary" : 30000

      }

    ]

  },

  {

    "name" : "Healthcare",

    "employees" : [

      {

        "name" : "Martin",

        "salary" : 45000

      },

      {

        "name" : "Smith",

        "salary" : 56000

      },

      {

        "name" : "Anderson",

        "salary" : 24000

      }

    ]

  },

  {

    "name" : "Mobility",

    "employees" : [

      {

        "name" : "Martin",

        "salary" : 45000

      },

      {

        "name" : "Smith",

        "salary" : 17000

      },

      {

        "name" : "Anderson",

        "salary" : 24000

      }

    ]

  }

]

This response is in array format and it is having all the departments with their name and employees set.

Let's start our filtration without which we can't live :)

#1 Filter the departments having employee salary less than 20000

Technically, We need all the departments having any of the employee's salary less than 20000.

    NSPredicate *predicate = [NSPredicate predicateWithFormat:

                                                         @"ANY employees.salary < %d",20000];

    

    NSArray *filteredArr = [arrDepartments filteredArrayUsingPredicate:predicate];

    

    NSLog(@"filteredArr : %@",filteredArr);

  filteredArr : (

        {

        employees =         (

                        {

                name = Tim;

                salary = 45000;

            },

                        {

                name = Smith;

                salary = 19000;

            },

                        {

                name = George;

                salary = 30000;

            }

        );

        name = Banking;

    },

        {

        employees =         (

                        {

                name = Martin;

                salary = 32000;

            },

                        {

                name = Smith;

                salary = 17000;

            },

                        {

                name = Anderson;

                salary = 24000;

            }

        );

        name = Mobility;

    }

  )

#2 Filter the departments having all the employees salary greater than 20000

    NSPredicate *predicate = [NSPredicate predicateWithFormat:

                                                          @"ALL employees.salary > %d",20000];

    

    NSArray *filteredArr = [arrDepartments filteredArrayUsingPredicate:predicate];

    

    NSLog(@"filteredArr : %@",filteredArr);

  filteredArr : (

        {

        employees =         (

                        {

                name = Martin;

                salary = 45000;

            },

                        {

                name = Smith;

                salary = 56000;

            },

                        {

                name = Anderson;

                salary = 24000;

            }

        );

        name = Healthcare;

    }

  )

    

#3 Filter the departments having none of the employees salary less then 20000

    NSPredicate *predicate = [NSPredicate predicateWithFormat:

                                                       @"NONE employees.salary < %d",20000];

    

    NSArray *filteredArr = [arrDepartments filteredArrayUsingPredicate:predicate];

    

    NSLog(@"filteredArr : %@",filteredArr);

  filteredArr : (

        {

        employees =         (

                        {

                name = Martin;

                salary = 45000;

            },

                        {

                name = Smith;

                salary = 56000;

            },

                        {

                name = Anderson;

                salary = 24000;

            }

        );

        name = Healthcare;

    }

  )

   

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