If you want to be able to access images.main
then you must define it explicitly:
interface Images {
main: string;
[key:string]: string;
}
function getMainImageUrl(images: Images): string {
return images.main;
}
You can not access indexed properties using the dot notation because typescript has no way of knowing whether or not the object has that property.
However, when you specifically define a property then the compiler knows that it’s there (or not), whether it’s optional or not and what’s the type.
Edit
You can have a helper class for map instances, something like:
class Map<T> {
private items: { [key: string]: T };
public constructor() {
this.items = Object.create(null);
}
public set(key: string, value: T): void {
this.items[key] = value;
}
public get(key: string): T {
return this.items[key];
}
public remove(key: string): T {
let value = this.get(key);
delete this.items[key];
return value;
}
}
function getMainImageUrl(images: Map<string>): string {
return images.get("main");
}
I have something like that implemented, and I find it very useful.