What is the process for defining functions with distinct data types while allowing variables to have multiple data types?

I am facing a declaration issue - or rather, a challenge in comprehending Typescript. Let me illustrate the scenario:

public migrationSource: Skater | Rink;
public migrationDestination: Skater | Rink;

public migrationMode: MigrationMode;

ngOnInit() {
    this.migrationSource = this.migrationMode == MigrationMode.Skater ? new Skater() : new Rink()
    this.migrationDestination = this.migrationMode == MigrationMode.Skater ? new Skater() : new Rink()
}

migrateSkater(skater1:Skater, skater2:Skater) {
    ...
}

migrateRink(rink1:Rink, rink2:Rink) {
    ...
}

Up to this point, everything seems fine. However, when attempting to invoke the function in my Angular code:

<ng-container *ngIf="migrationMode == mode.SKATER">
    <button (click)="migrateSkater(migrationDestination, migrationSource)">
        ...
    </button>
</ng-container> 

<ng-container *ngIf="migrationMode == mode.RINK">
    <button  (click)="migrateRink(migrationDestination, migrationSource)">
        ...
    </button>
</ng-container>

An error message is displayed as follows:

error TS2345: Argument of type 'Skater | Rink' is not assignable to parameter of type 'Skater'.
Type 'Rink' is not assignable to type 'Skater'.

I comprehend the essence of this error message, but I am unsure how to rectify it. Thus far, I resorted to changing the data types of migrateSkater and migrateRink to any, however, this solution does not align with my intention. Is there a method to explicitly define the data types of the functions in Typescript and if so, how can I achieve this?

angulartypescripttypescript-generics

Answer №1

To tackle this problem, consider leveraging the power of classes and inheritance:

class Ingredient {
  public name: string;
};

class Vegetable extends Ingredient {
  public weight: number;
}

class Fruit extends Ingredient {
  public quantity: number;
}

Next, create a function that can work with either Vegetable or Fruit parent classes:

  updateIngredient(i1:Ingredient, i2: Ingredient){

  }

In the child classes, you have the flexibility to include functions for duplicating content in a more comprehensive manner.

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