I have an Angular project in which i defined some classes Classroom and Student and Address.
The problem in Angular when i use the bidirectional binding in edit-student-component.html where an address reference is null or undefined it does not work anymore.

<span  class="field mr-3">
  <input pInputText id="student-address-street" placeholder="Student Street" [(ngModel)]="selected.address.street"/>
</span>

this code throws an error in case address is null or undefined, so i thought i would define setters and getters to get and set the student address.

export class Classroom {
  id: number
  students : Student[];
}

export class Student {
  id: number
  firstname: string
  lastname: string
  age: number

  get address() : Address {
    if (this.address) {
      return this.address
    } else {
      return new Address()
    }
  }

  set address(address: Address) {
    if (address) {
      this.address = address
    } else {
      this.address = new Address()
    }
  }
}

export class Address {
  id: number
  street: string
  city: string
  country: string
  postcode: string
}

however when i do this i get a compile error in the student-edit-component.ts at this line:

const observer: Observer<Student> = {
  next:  (data: any)  => {
    ...
    this.students.splice(index, 1, {...this.editStudent})    <<<<<<< erronous line 
    // this.editStudent is the selected student which is beeing edited  
    ...

TS2345: Argument of type ‘{ id: number; firstname: string; lastname: string; age: number;}’ is not assignable to parameter of type ‘Student’.
Type ‘{ id: number; firstname: string; lastname: string; age: number; }’ is missing the following properties from type ‘student’: address