Error with TypeScript syntax: declarative array with methods

Question

I have a problem with TypeScript syntax in my Angular 4 project. If I create a normal class, such as:

export class MyClass {
  field1: string;
  field2: number;
  field3: boolean;

  myMethod() {
   this.field2 = this.field2 + 2;
  }
}

I can't declare an array of MyClass elements with this syntax:

myclassarray: MyClass[] = [{
  field1: 'hello',
  field2: 3,
  field3: false
}];

Because in my class there is an instance method and not a static method. The question is: how can I declare an array of elements that also include non-static methods that are useful to me?

I also don't understand the syntax that allows you to initialize these items in a declarative way.

because I want methods that modify the data fields of my class instance — claudioz
– claudioz, Commented Sep 7, 2017 at 12:47
Is it language issue or your problem not understanding principles of OOP? If you need array of objects with methods - you maust use new MyClass() syntax. If you want to initialize properties - use constructor. If you have "too many" properties - use constructor that accepts interface (constructor(dto: MyClassInterface){ this = Object.assign({}, dto);}). — A. Tim
– A. Tim, Commented Sep 7, 2017 at 12:52

Saravana · Accepted Answer · 2017-09-07 12:48:18Z

3

You can use Object.assign to assign the object literal to an instance of MyClass:

myclassarray: MyClass[] = [
    Object.assign(new MyClass(), {
        field1: 'hello',
        field2: 3,
        field3: false
    })
];

answered Sep 7, 2017 at 12:48

Saravana

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Comments

msanford · Accepted Answer · 2017-09-07 13:05:03Z

0

Since you're using a class, why not use a constructor?

class MyClass {
    constructor(public field1: string, public field2: number, public field3: boolean) {}

    myMethod() {
        this.field2 = this.field2 + 2;
    }

    show() {
        console.log(this.field2);
    }
}

let myclassarray = new MyClass(
    'hello', 3, false
);

You can then call them like so:

myclassarray.myMethod();
myclassarray.show(); // logs 5

answered Sep 7, 2017 at 13:05

msanford

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Comments

Rohan Fating · Accepted Answer · 2017-09-07 12:54:47Z

-1

You need to create object of MyClass first and then intialize values then push into array.

myclassarray: Array<MyClass> = [];
myClass: MyClass = new MyClass();
    myClass.field1 ='';
    myClass.field2 =1;
    myClass.field3 = false;


myclassarray.push(myClass);

answered Sep 7, 2017 at 12:54

Rohan Fating

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