What is the best way to assign or convert an object of one type to another specific type?

Question

What is the best way to assign or convert an object of one type to another specific type?

So here's the scenario: I have an object of type 'any' and I want to assign it an object of type 'myResponse' as shown below.

    public obj: any;
    public set Result() {
        obj = myResponse;
    }

Now, in another function, I need to convert this generic 'any' type to my specific type - let's call it 'MyResponse'. Here's what I tried:

public myFunction(){
    let x: MyResponse = (MyResponse) obj;
    conosle.log(x.somePropoerty);
}

I explored various methods like using angular brackets for casting and Object.assign, but unfortunately, they didn't work in this case. In addition, just to give you a clearer picture, here is how the 'MyResponse' class looks like:

export class MyResponse{
    public property1: string;
    public property2: number;
    //some other code
}

javascript angular typescript

Answer 1

Answer №1

TypeScript does not support casting but allows for type assertions. To declare that obj is of type MyResponse, you can use the following syntax:

let x: MyResponse = obj as MyResponse;

It's important to remember that this assertion is only checked at compile-time. If your obj turns out not to be a valid instance of MyResponse during runtime, this method will not be effective.

Answer 2

TypeScript does not support casting but allows for type assertions. To declare that obj is of type MyResponse, you can use the following syntax:

let x: MyResponse = obj as MyResponse;

It's important to remember that this assertion is only checked at compile-time. If your obj turns out not to be a valid instance of MyResponse during runtime, this method will not be effective.

Answer 3

Answer №2

When working with TypeScript, casting (referred to as Type assertions by Microsoft) can be achieved in two different ways.

Imagine we have the following object definition:

class MyClass {
    public someMethod:void() {
         console.log("method invoked");
    }
    public static staticMethod(object: MyClass) {
         console.log("static method");
         object.someMethod();
    }
}

The first method of casting is akin to how it's done in Java. You use the <> signs for this approach.

let someVariable: any = new MyClass();
someVariable.someMethod(); //will not compile
MyClass.staticMethod(someVariable); //will not compile

(<MyClass> someVariable).someMethod(); //will compile
MyClass.staticMethod(<MyClass> someVariable); //will compile

The second method is demonstrated by @Saravana (where the as keyword is used):

//all lines below will compile
let someVariable: any = new MyClass();
let another: MyClass = someVariable as MyClass;
(someVariable as MyClass).someMethod(); 

MyClass.staticMethod(someVariable as MyClass);

For more details, you can refer to this link: https://www.typescriptlang.org/docs/handbook/basic-types.html#type-assertions

Answer 4

When working with TypeScript, casting (referred to as Type assertions by Microsoft) can be achieved in two different ways.

Imagine we have the following object definition:

class MyClass {
    public someMethod:void() {
         console.log("method invoked");
    }
    public static staticMethod(object: MyClass) {
         console.log("static method");
         object.someMethod();
    }
}

The first method of casting is akin to how it's done in Java. You use the <> signs for this approach.

let someVariable: any = new MyClass();
someVariable.someMethod(); //will not compile
MyClass.staticMethod(someVariable); //will not compile

(<MyClass> someVariable).someMethod(); //will compile
MyClass.staticMethod(<MyClass> someVariable); //will compile

The second method is demonstrated by @Saravana (where the as keyword is used):

//all lines below will compile
let someVariable: any = new MyClass();
let another: MyClass = someVariable as MyClass;
(someVariable as MyClass).someMethod(); 

MyClass.staticMethod(someVariable as MyClass);

For more details, you can refer to this link: https://www.typescriptlang.org/docs/handbook/basic-types.html#type-assertions

Answer 5

Answer №3

Converting an object into a specific "Type" requires modifying the prototype of the object by instantiating a new Constructor function and copying over all existing properties.

If not done properly, type assertion will only offer validation at compile-time. This could lead to issues such as encountering an undefined "someMethod" during runtime.

Answer 6

Converting an object into a specific "Type" requires modifying the prototype of the object by instantiating a new Constructor function and copying over all existing properties.

If not done properly, type assertion will only offer validation at compile-time. This could lead to issues such as encountering an undefined "someMethod" during runtime.

What is the best way to assign or convert an object of one type to another specific type?

Answer №1

Answer №2

Answer №3

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