How would one make multiple exception classes inherit from one parent class?

Question

So far I have this...

class MembersController < ApplicationController rescue_from Mailchimp::Exception::DataException, Mailchimp::Exception::APIKeyError, Mailchimp::Exception::NotFound, Mailchimp::Exception::Duplicate, Mailchimp::Exception::MissingField, Mailchimp::Exception::BadRequest, Mailchimp::Exception::UnknownAttribute, Mailchimp::Exception::MissingId, with: :error def error(e) puts 'Message: ' + e.message puts 'Type: ' + e.type puts 'Title: ' + e.title e.errors.each do |error| puts 'Field: ' + error['field'] puts 'Message: ' + error['message'] end if e.errors # Respond to the HTTP POST request by passing the errors return render_with(500, e.message, e.errors) end private def render_with(status_code, message, errors='none') if errors == 'none' status = 'success' success = true else status = 'error' success = false end render json: { :status => status, :success => success, :message => message, :errors => errors, :params => params.as_json }, status: status_code end end

In an attempt to make it DRY, I have done this...

class MembersController < ApplicationController mailchimpExceptions = [ 'DataException', 'APIKeyError', 'NotFound', 'Duplicate', 'MissingField', 'BadRequest', 'UnknownAttribute', 'MissingId' ] exceptions = Array.new mailchimpExceptions.each do |exception| exceptions << "Mailchimp::Exception::#{exception}" end rescue_from *exceptions, with: :error def error(e) puts 'Message: ' + e.message puts 'Type: ' + e.type puts 'Title: ' + e.title e.errors.each do |error| puts 'Field: ' + error['field'] puts 'Message: ' + error['message'] end if e.errors # Respond to the HTTP POST request by passing the errors return render_with(500, e.message, e.errors) end private def render_with(status_code, message, errors='none') if errors == 'none' status = 'success' success = true else status = 'error' success = false end render json: { :status => status, :success => success, :message => message, :errors => errors, :params => params.as_json }, status: status_code end end

I am wondering if all the exceptions could by under one class, so that only one class is called like rescue_from MailchimpExceptions, with: :error. This answer by mgolubitsky suggests it is possible, but I have no idea how to go about it.

I am using gem 'mailchimp_api_v3'.

Yeah, it's really an oversight on mailchimp's part. I see no possible reason not to have a common error class for your gem. Probably, your best bet is to do what @mudasobwa is suggesting. — Sergio Tulentsev
– Sergio Tulentsev, Commented Mar 15, 2017 at 11:07
Maybe there was a reason for this, I have no idea. Note that most of them inherit from DataException. So you can rescue that one and the few rogues. — Sergio Tulentsev
– Sergio Tulentsev, Commented Mar 15, 2017 at 11:31
Now, RuntimeError is one of the system classes and is too generic. Don't rescue that one. — Sergio Tulentsev
– Sergio Tulentsev, Commented Mar 15, 2017 at 12:18

thaleshcv · Accepted Answer · 2017-03-15 11:10:50Z

2

Take a look at https://github.com/dominicsayers/mailchimp_api_v3#exception-handling

It says:

All exceptions will be subclasses of Mailchimp::Exception

try rescue_from Mailchimp::Exception, with: :error

edited Mar 15, 2017 at 11:10

answered Mar 15, 2017 at 10:55

thaleshcv

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1 Comment

ckhatton Over a year ago

I'm afraid that doesn't work - It doesn't rescue the exception. I seem to remember trying that before, as I also read that line in the README.md

Aleksei Matiushkin · Accepted Answer · 2017-03-15 15:46:29Z

2

I have no idea about mailchimp itself, but I can generally suggest how to make it DRY properly:

EXCEPTIONS = %w| DataException APIKeyError NotFound Duplicate MissingField BadRequest UnknownAttribute MissingId|.map { |e| Mailchimp::Exception.const_get(e) } rescue_from *EXCEPTIONS, with: :error

Or, to rescue_from all exceptions, defined in Mailchimp::Exception at once:

EXCEPTIONS = Mailchimp::Exception.constants.map do |e| Mailchimp::Exception.const_get(e) end.select { |e| e.is_a?(Class) && e < Exception }

edited Mar 15, 2017 at 15:46

answered Mar 15, 2017 at 11:05

Aleksei Matiushkin

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7 Comments

ckhatton Over a year ago

Real tidy! Like it! Though the latter didn't work, I think because of an error on this gem page

ArgumentError ({"RestClient::ResourceNotFound"=>Mailchimp::Exception::NotFound, "RestClient::Unauthorized"=>Mailchimp::Exception::APIKeyError} must be an Exception class or a String referencing an Exception class):

Aleksei Matiushkin Over a year ago

Simply filter out everything that is not an exception. I have the answer updated.

ckhatton Over a year ago

That doesn't pick up anything - In other words, it produced an empty array

Aleksei Matiushkin Over a year ago

Oh, indeed. e is a class there, not instance, please see an update.

ckhatton Over a year ago

Now TypeError (no implicit conversion of Class into Hash):. Maybe the Class name needs to be grabbed as a string?

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