My goal is to update an object with a specific interface programmatically. I have defined the interface as follows:
interface ITypes {
num: number;
str: string;
bol: boolean;
};
const obj: Partial<ITypes> = {}; // This is the object I want to update programmatically
I am looking for a way to specify a key and a val in order to update my obj. The key should be limited to one of the keys from the ITypes interface, and the value should match the type specified at the selected key from the interface. Initially, I achieved this by using the following code:
const key: keyof ITypes = "num"; // The key must be from the ITypes interface
const val: ITypes[typeof key] = 1; // The val must match the type specified at 'num' - 'number'
obj[key] = val;
Although the above method works, I now aim to define both the key and val within an object, which requires me to create an interface. However, I encountered challenges with defining the type for val. Here's what I've attempted so far:
interface IUpdatePayload {
key: keyof ITypes;
val: ITypes[typeof this.key]; // The error 'Type 'any' cannot be used as an index type.' occurs here
};
const updatePayload: IUpdatePayload = {key: "num", val: "1"}; // It should flag an error that 'val' is not a number
obj[updatePayload.key] = updatePayload.val;
I tried referencing the interface's key type using typeof this.key, as suggested in this answer, but it resulted in the error
Type 'any' cannot be used as an index type.val to adopt the type determined by key as outlined in the ITypes interface?