Can one obtain a comprehensive array of interfaces or a detailed map showcasing all their variations?

I have developed a method that takes in an object containing data and returns an object that adheres to a specific interface.

interface FireData {
    id: EventTypes;
    reason?: string;
    error?: string;
}

enum EventTypes {
    eventType1 = "ev1",
    eventType2 = "ev2,
    ...
}

interface EventComposedData {
    key1: string;
    key2: boolean;
    key3: EventTypes;
    "event-value": string;
}

track(fireData: FireData): EventComposedData {
    const composedData = composeSomehowECD(fireData);
    sendTracking(composedData);
}

I encountered a situation where I needed to provide data in the fireData object to override the default values returned by composeSomehowECD.

To achieve this, I proceeded as follows:

interface FireData {
    id: EventTypes;
    reason?: string;
    error?: string;
    eventData?: {
        [key in keyof EventComposedData]?: any
    }
}

Currently, when I execute:

track({
    eventData: {
        key1: "4"
    }
});

key1 has the type any, which can potentially lead to incorrect values affecting the final output. I am seeking a way to retrieve all the types of an interface (perhaps something like:

[key in keyof EventComposedData]?: typesof EventComposedData
) or a more efficient method to define the key-value pairs.

One alternative approach could be:

interface FireData {
   ...
   eventData: EventComposedData;
}

However, what if I want to allow properties to be accessed like an index?

For instance:

const eventData: { [key in keyof EventComposedData]: any } = {};
eventData["event-value"]: 5

track(eventData);

In such a scenario, event-value is always assigned the type any, causing the same issue as before. It becomes challenging to assign a specific type instead of any due to the multitude of possible types. Thank you.

Answer №1

Typically, a mapped type is recommended in this scenario. These types allow you to modify which keys are present in an object type and adjust their values. In this case, you aim to have a type similar to EventComposedData, but with all properties being optional.

Here is an example of how you can achieve this:

  eventData?: {
    [K in keyof EventComposedData]?: EventComposedData[K]
  };

Alternatively, TypeScript offers a predefined mapped type called Partial that accomplishes the same thing. Instead of creating your own, you can use it directly like this:

  eventData?: Partial<EventComposedData>;

Both approaches are equivalent: you can opt for Partial directly, or utilize the mapped type itself if you need to perform more complex operations (e.g., enforcing a specific property, excluding certain properties).

For further experimentation, you can check out this TypeScript playground demo

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