How to instantiate an object in Angular 4 without any parameters

Currently, I am still getting the hang of Angular 4 Framework. I encountered a problem in creating an object within a component and initializing it as a new instance of a class. Despite importing the class into the component.ts file, I keep receiving an error indicating that it expects 4 arguments but has none. Can someone lend me a hand with this?

The class structure for my student is provided below:

export class Student {



  constructor(
    public _id: number,
    public first_name :string,
    public last_name: string,
    public email : string

  ){}
}

The issue lies in the component file in the following section:

export class StudentNewComponent implements OnInit {
  newStudent= new Student();

  createStudentEvent= new EventEmitter();
  
  constructor() { }

  ngOnInit() {
  }

  create(){
      this.createStudentEvent.emit(this.newStudent);
      this.newStudent = new Student();
  }
}

In the code snippet above, the error occurs in the second line

newStudent= new Student();

as well as the last line

this.newStudent = new Student();

I prefer not to instantiate the newStudent object since it will be populated from a different component in the application.

Answer №1

Here is an example:

export class Person {
    constructor(
        public id?: number,
        public firstName?: string,
        public lastName?: string,
        public email?: string
    ) { }
}

To create a new object, use

newPerson: Person = new Person();

Answer №2

In TypeScript, you have the ability to designate constructor arguments as optional by simply adding a question mark (?) at the end of the parameters that should be optional. For instance, if we want the last name parameter in the example below to be optional:

function buildName(firstName: string, lastName?: string) {
    if (lastName)
        return firstName + " " + lastName;
    else
        return firstName;
}
let result1 = buildName("Bob");                  // This now works properly
let result2 = buildName("Bob", "Adams", "Sr.");  // Error - too many parameters provided
let result3 = buildName("Bob", "Adams");         // Just right!

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