CODEWITHSUNDEEP
javascriptbluebird
Maksym
Maksym

Reputation: 3428

Handling exception in Bluebird

function ApiError(response) {
  this.message = 'API error';
  this.response = response;
}

ApiError.prototype = Object.create(Error.prototype);
ApiError.prototype.constructor = ApiError;
ApiError.prototype.name = 'ApiError';

export default ApiError;

I have this custom exception and I throw it at some point, but when I try to catch it in promise like

import ApiError from './ApiError';
...
.catch(ApiError, (e) => {
    console.log('api error');
})
.catch((e) => {
    console.log(e); <= this is undefined(in ApiError)
});

the error is delegated to generic catch with error saying that message cannot be assigned to undefined(this=undefined in ApiError), what am I doing wrong here ?

EDIT: The problem was actually the fact that I was not returning an instance of Bluebird promise, but Node Promise(using fetch), I resolved it by wrapping fetch inside Bluebird Promise.resolve.

Upvotes: 2

Views: 140

Answers (2)

Maksym
Maksym

Reputation: 3428

The problem was actually the fact that I was not returning an instance of Bluebird promise, but ES6 Promise(using fetch), I resolved it by wrapping fetch inside Bluebird Promise.resolve.

Upvotes: 0

jfriend00
jfriend00

Reputation: 707666

That error sounds like you aren't creating the instance of your ApiError object properly.

When you throw one of your errors, it should be:

throw new ApiError(xxx);

Note, the new that must be used. The specifics of your error make it appear like you aren't using the new.

Alternatively, you could change the implementation of your ApiError constructor so that you could do;

throw ApiError(xxx);

But, you'd have to change ApiError to detect whether it was called with new or not and if not, then call new itself.

function ApiError(response) {
  if (!(this instanceof ApiError)) {
      return new ApiError(response);
  }
  this.message = 'API error';
  this.response = response;
}

Or, in ES6, you can use the new.target option:

function ApiError(response) {
  if (!new.target) {
      return new ApiError(response);
  }
  this.message = 'API error';
  this.response = response;
}

Upvotes: 2

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