在同一接口中访问接口属性值

Question

I'm wondering if it's possible to access an interface prop value in the same interface declaration in order to set the types dynamically.

I'm trying to do something like this:

export type MethodNames = "IsFallmanagerUpdateAllowed" | "UpdateStammFallmanager";

export interface IsFallmanagerUpdateAllowed {
  plcParameter : StammFallmanagerParameter
}

export interface UpdateStammFallmanager {
  plcParameter : StammFallmanagerParameter
}

export interface ServerTaskParam<T> extends system.ServerTaskParam<T> {
  name       : `${Class.NAME}`,
  methodName : MethodNames,
  paramObj   : // here depending on the passed methodname type should be IsFallmanagerUpdateAllowed or UpdateStammFallmanager
  // paramObj   : T -> this is what I use atm but I want to make it more dynamic
}

Note that there could be more MethodNames .

What I want to achieve is that when passing name and methodName the intellisense should be able to tell me directly which type of object should be passed as paramObj .

It should be something like this if possible:

export interface ServerTaskParam extends system.ServerTaskParam {
  name       : `${Class.NAME}`,
  methodName : MethodNames,
  paramObj   : [ methodName ] -> use methodName value to refer to one or the other interface in the same namespace (pseudo syntax)
}

I'm searching the net for a while now but couldn't find anything. Is this even possible?

Answer 1

You could create a composite type holding every possible interface so you can use this "higher type" with its keys like so:

export interface IsFallmanagerUpdateAllowed {
  plcParameter : StammFallmanagerParameter
}

export interface UpdateStammFallmanager {
  plcParameter : StammFallmanagerParameter
}

interface Methods {
  IsFallmanagerUpdateAllowed: IsFallmanagerUpdateAllowed;
  UpdateStammFallmanager: UpdateStammFallmanager;
}

export interface ServerTaskParam<K extends keyof Methods> extends system.ServerTaskParam<T> {
  name       : `${Class.NAME}`,
  methodName : K,
  paramObj   : Methods[K]
};

Answer 2

I think what you need is just a union:

export type ServerTaskParam = ({
  name       : `${Class.NAME}`,
  methodName : "IsFallmanagerUpdateAllowed",
  paramObj   : IsFallmanagerUpdateAllowed
} | {
  name       : `${Class.NAME}`,
  methodName : "UpdateStammFallmanager",
  paramObj   : UpdateStammFallmanager
}) & system.ServerTaskParam

Playground