As part of a project, I have created two classes:
ParentClasschildrenClasswhich extends theParentClassclass
Displayed below is the code for my ParentClass:
interface ConfSetup<T extends boolean> {
enabled: T;
permissions: bigint[];
location: string;
}
interface AssistanceInfo {
name: string;
description: string
category: string;
id: number;
}
interface ParentClassConfiguration<T extends boolean> {
confData: ConfObj<T>;
assistance: HelpObj;
}
type ParentClassParameters<T extends boolean> = AssistanceInfo & ConfObj<T>;
class ParentClass<T extends boolean> {
config: ConfObj<T>;
assist: HelpObj;
constructor({ enabled, permissions, location, name, description, category, id }: ParentClassParameters<T>) {
this.config = {
enabled, permissions, location
};
this.assist = {
name, description, category, id
}
}
}
Following that, in the ParentClass constructor, I set appropriate values to the class properties.
In the context of the childrenClass, I extend the ParentClass with necessary details. The goal is to modify the type of a parameter in the ChildrenClass class when the value of ParentClass.conf.enabled is true.
I attempted the following code (for the children class):
interface ChildConfigInterface<T extends ParentClass<any>> {
isEnabled: () => boolean;
name: string;
description: string | (T["conf"]["enabled"] extends false ? undefined : never);
}
class ChildrenClass extends ParentClass<true> {
constructor() {
super({
enabled: true,
permissions: [],
location: '',
name: '',
description: '',
category: '',
id: 0
});
}
operate(data: ChildConfigInterface<ChildrenClass>) {
return data.description;
}
}
So, in this scenario, if we set the ParentClass value to true, the type of data.description should be string. Conversely, if enabled is set to false, then the type of data.description will be string | undefined.
I hope this explanation clarifies the concept. For further understanding, please refer to the provided minimal reproducible example on TS playground. The operate method within the ChildrenClass should execute error-free, without adding any conditional statements or altering the method's return type.