Should try catch TypeScript assertion function?

Question

I create a TS assertion function, Later, I use it before passing the request DTO to the API service in a UI event handler.

function assertIsGetCampaignPackageReqDTO(
  value: any,
): asserts value is GetCampaignPackageRuquestDTO {
  if (!value.campaignId || !value.packageCode) {
    throw new Error('campaignId or packageCode is empty!');
  }
}

const onSearchFormSubmit = async (e: FormEvent<HTMLFormElement>) => {
  e.preventDefault();
  try {
    assertIsGetCampaignPackageReqDTO(searchCondition);
    const { value } = await getCampaignPackageQuery.execute(searchCondition);
    if (value?.code === '0') {
      setCampaignPackages(campaignPackages.concat(value.result));
    }
  } catch (error) {
    message.error(error.message);
  }
};

Should I use try...catch statement with the assertion function and show the error message to users? Or, I should validate the legality(if statement) of the request DTO before using the assertion function. The assertion function is only used for passing the TSC check?

Or this:

function assertIsGetCampaignPackageReqDTO(
  value: any,
): asserts value is GetCampaignPackageRuquestDTO {
  if (!value.campaignId || !value.packageCode) {
    throw new Error('value is not GetCampaignPackageRuquestDTO');
  }
}

const onSearchFormSubmit = async (e: FormEvent<HTMLFormElement>) => {
  e.preventDefault();
  if (!searchCondition.campaignId || !searchCondition.packageCode) {
    return message.error('campaignId or packageCode is empty!');
  }
  assertIsGetCampaignPackageReqDTO(searchCondition);
  const { value } = await getCampaignPackageQuery.execute(searchCondition);
  if (value?.code === '0') {
    setCampaignPackages(campaignPackages.concat(value.result));
  }
};

irous · Accepted Answer · 2022-09-07 11:13:21Z

1

I assume all you want is to catch exceptions instead of letting your program be crashed.

If the code in function assertIsGetCampaignPackageReqDTO is exactly the same as in if condition, then you should choose one of those methods. I prefer using if condition for simplicity.
If there are other checks in assert function, you should use both: try catch and if condition. Using if if you want to catch separate cases such as campaignId and packageCode (as shown in your code). And using try catch to catch other failure cases.

if (!searchCondition.campaignId || !searchCondition.packageCode) {
    return message.error('campaignId or packageCode is empty!');
}

try {
    assertIsGetCampaignPackageReqDTO(searchCondition);
    const { value } = await getCampaignPackageQuery.execute(searchCondition);
    if (value?.code === '0') {
      setCampaignPackages(campaignPackages.concat(value.result));
    }
} catch (error) {
    message.error(error.message);
}

edited Sep 7, 2022 at 11:13

answered Sep 2, 2022 at 11:16

irous

4994 silver badges9 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Amit Kumar Over a year ago

Additional info along with the above answer, You could typecast any variable using as <type> that will be the tsc check. The code inside assert function is actually checking if the necessary property are present in object, so it's a check in javascript too!

Collectives™ on Stack Overflow

Should try catch TypeScript assertion function?

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related