Make sure to include all enum type values within the function's body to ensure comprehensive coverage

Question

Make sure to include all enum type values within the function's body to ensure comprehensive coverage

I am defining an enumeration called ApiFunctions with values like "HIDE", "SET_READ_ONLY", and "DESCRIPTION". Also, I have a type ValueOfApiFunction that should include all values of ApiFunctions.

Additionally, I have a logic that listens for messages on the window event. Within this logic, there is a forEach loop checking for changes in certain fields based on the action provided. I want to ensure that all values from my ApiFunctions enum are handled within this loop to avoid any errors during compilation.

Thank you for your assistance.

javascript typescript compiler-errors logic

Answer 1

Answer №1

While TypeScript lacks native functionalities to enforce specific logic within a codebase, it primarily focuses on preventing incorrect manipulation of objects rather than scrutinizing the actual logic being implemented. However, there exists a workaround that allows you to ensure that certain logic is executed for every possible enum value:

One approach is to create a JSON object that contains all enum values as keys, with each key corresponding to a function representing the desired logic for that enum value:

const fieldToAction: { [key in ValueOfApiFunction]: (field?: Field) => void } = {
  "HIDE": (field?: Field) => field?.setVisible(false),
  "SET_READ_ONLY": (field?: Field) => field?.setName("This field is now read only"),
  "DESCRIPTION": (field?: Field) => field?.setName("This field is now read only"),
}

(The Field type could vary and was not specified in the provided example)

To execute this logic for each enum value, simply call it within a forEach loop like so:

fieldToAction[change.action](field);

You can find a working example illustrating this behavior in the TypeScript playground via this link.

Answer 2

While TypeScript lacks native functionalities to enforce specific logic within a codebase, it primarily focuses on preventing incorrect manipulation of objects rather than scrutinizing the actual logic being implemented. However, there exists a workaround that allows you to ensure that certain logic is executed for every possible enum value:

One approach is to create a JSON object that contains all enum values as keys, with each key corresponding to a function representing the desired logic for that enum value:

const fieldToAction: { [key in ValueOfApiFunction]: (field?: Field) => void } = {
  "HIDE": (field?: Field) => field?.setVisible(false),
  "SET_READ_ONLY": (field?: Field) => field?.setName("This field is now read only"),
  "DESCRIPTION": (field?: Field) => field?.setName("This field is now read only"),
}

(The Field type could vary and was not specified in the provided example)

To execute this logic for each enum value, simply call it within a forEach loop like so:

fieldToAction[change.action](field);

You can find a working example illustrating this behavior in the TypeScript playground via this link.

Answer 3

Answer №2

To utilize the 'never' type effectively, you can implement it in the following way:

event.data.changes.forEach((change: { fieldId: string, action: ValueOfApiFunction }) => {
    const field = api.getFieldById(change.fieldId);
    if(change.action === "HIDE") {
        field?.setVisible(false);
    }
    else if(change.action === "SET_READ_ONLY") {
        field?.setName("This field is now read only")
    } else {
        const _shouldNeverBeReached: never = change.action
    }
    
})

If you happen to forget handling a change.action, the type will not become never and thus it won't compile.

UPDATE : for a more explicit message:

const exhaustiveCheck = <T extends any>(t: T extends never ? never : "One of the cases was not handled") => {
  throw new Error("One of the cases was not handled")
}

and then

    } else {
        exhaustiveCheck(change.action)
    }

Answer 4

To utilize the 'never' type effectively, you can implement it in the following way:

event.data.changes.forEach((change: { fieldId: string, action: ValueOfApiFunction }) => {
    const field = api.getFieldById(change.fieldId);
    if(change.action === "HIDE") {
        field?.setVisible(false);
    }
    else if(change.action === "SET_READ_ONLY") {
        field?.setName("This field is now read only")
    } else {
        const _shouldNeverBeReached: never = change.action
    }
    
})

If you happen to forget handling a change.action, the type will not become never and thus it won't compile.

UPDATE : for a more explicit message:

const exhaustiveCheck = <T extends any>(t: T extends never ? never : "One of the cases was not handled") => {
  throw new Error("One of the cases was not handled")
}

and then

    } else {
        exhaustiveCheck(change.action)
    }

Make sure to include all enum type values within the function's body to ensure comprehensive coverage

Answer №1

Answer №2

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