How to Properly Initialize a Variable for Future Use in a Component?

After initializing my component, certain variables remain unassigned until a later point. I am seeking a way to utilize these variables beyond the initialization process, but I am unsure of how to do so. Below is my attempted code snippet, which throws an error stating 'Type 'Map' is not assignable to type 'undefined'.


    export class DummyComponent implements AfterViewInit {
      map = null;
      mousePosition = undefined;

      ngAfterViewInit(): void {

        this.map = new Map({
          target: 'map',
          layers: [layer],
          view: view
        });
      }

      update(){ 
        this.map.on(...) => {...}
      }
    

Answer №1

It appears that you are encountering a type safety issue. When starting a new Angular project, a tsconfig.json file is created with the default setting strict set to true. This setting influences the noImplicitAny setting, which is also set to true. This means that if you do not explicitly define the type of a variable or field, it will default to the type of its assigned value.

In your case, by assigning null to map, the field's type defaults to null since you did not specify a type when declaring it. To resolve this, you can specify the allowed types for the map field to be both null and Map.

map: Map | null = null;

With this change, you can now assign either value to the field. However, remember that when accessing the field in your code, you need to assert the type if multiple types are allowed. For example:

otherMethod(): void {
  if (this.map !== null) {
    this.map. // perform operations on the map field
  }
}

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