class ParentClass
def run
rescue StandardError => e
p 'catch in parent class'
end
end
class ChildClass < ParentClass
def run
rescue ArgumentError => e
p 'catch in child class'
end
end
Kindly review above code, I have a series of children classes.
instance = ChildClass.new
instance.run
when instance run and meet ArgumentError, ChildClass will handle it. If not, since the parent class will catch all general StandardError, any error not caught in ChildClass, will be caught in parent class eventually.
How to implement the above logic?
Related
Say I have a custom error class that inherits from a parent error class. How can I add an attribute to that class, so something like:
class CustomError <CustomParentErrorClass
status: 500
end
So that in my controller I could do something like
rescue CustomErroClass => e
head(e.status)
I essentially want to access my attribute from my rails error class from my controller but am not sure how to. Any thoughts?
You can define attributes on the CustomError class just like any other error class
class CustomError < StandardError
attr_reader :status
def initialize(status)
#status = status
end
end
Here is a sample usage
begin
raise CustomError.new(500)
rescue CustomError => e
head(e.status)
end
If the attributes are hard-coded and do not need to be passed from where the error is raised, you can hard-code it
class CustomError < StandardError
attr_reader :status
def initialize
#status = 500 # you can also define a constant instead of attribute if the value will be a constant
end
end
That said, a word of caution for the example that you shared:
You are defining a status attribute. I am guessing this error will be raised from your model or service class and rescued in the Controller. If this is the case, consider avoiding coupling the model class to the HTTP status that the controller should return.
I have a class that has N methods.
class MyClass
def self.method_one(params)
#specific code
end
def self.method_two(params)
#specific code
end
end
I need to add the same code for each method created in that class. I need to put the code between "begin and rescue"
I tried the following, but I did not succeed:
class MyClass < BaseClass
add_rescue :method_one, :method_two, Exception do |message|
raise message
end
def self.method_one(params)
#specific code
end
def self.method_two(params)
#specific code
end
end
I created a method to change the methods
class BaseClass
def self.add_rescue(*meths, exception, &handler)
meths.each do |meth|
old = instance_method(meth)
define_method(meth) do |*args|
begin
old.bind(self).call(*args)
rescue exception => e
handler.call(e)
end
end
end
end
end
I always get the error message: undefined method `method_one 'for Myclass: Class
MyClass#method_one is a class method or, in other words, the instance method of MyClass.singleton_class. That said, we can Module#prepend the desired functionality to MyClass.singleton_class:
def self.add_rescue(*meths, exception, &handler)
mod =
Module.new do
meths.each do |meth|
define_method meth do |*args, &λ|
begin
super(*args, &λ)
rescue exception => e
handler.(e)
end
end
end
end
MyClass.singleton_class.prepend(mod)
end
I am using the interactor gem in my rails project. When one of the interactors within the organizer fails, the rollback method is called. The question is, is there any way this method can be aware of why the interactor failed?
Example:
def call
context.fail! error: 'Some error'
end
def rollback
# I want to access 'Some error' here
end
You can just access the context inside rollback method. There is one catch - rollback of the "current" interactor won't be invoked. Take a look at the following code:
require "interactor"
class Foo
include Interactor
def call
end
def rollback
p "#{context.error} from Foo"
end
end
class Bar
include Interactor
def call
context.fail!(error: "error!")
end
def rollback
p "#{context.error} from Bar"
end
end
class FooBar
include Interactor::Organizer
organize Foo, Bar
end
FooBar.call
it produces "error! from Foo" as the response. Bar throws an exception so FooBar organizer goes back to the Foo and calls its rollback method. context is shared so you have access to everything that was set before.
In my Rails 4 app I have a Service object that handles communication with Stripe Payments Processor. I want it as a service object so that multiple Controllers/Models can utilize the methods within it.
However, I also need to be able to trap errors when communicating with the Stripe API which then causes the problem as the errors need to be assigned to a particular object.
Here is a method in my StripeCommunicator.rb class:
def create_customer(token,object)
customer = Stripe::Customer.create(:description => 'Accommodation', :email => object.email, :card => token)
return customer
rescue Stripe::CardError => e
#account.errors.add :base, e.message
false
end
as you can see - the errors are being added to the #account object - which essentially renders it useless when I want to use this method from another controller with a View that refers to another object to display errors.
Any ideas?
Simplest thing is to just pass the #account instance in as another argument. Errors is going to be on any model instance, e.g.
def create_customer(token,object,model_instance)
Stripe::Customer.create(description: 'Accommodation', email: object.email, card: token)
# return customer <- don't need this. whatever is last evaluated will be returned
rescue Stripe::CardError => e
model_instance.errors.add :base, e.message
false
end
If you were doing the error handling in the controller instead of a service object, you could take advantage of rescue_from which can handle exceptions falling out from action methods, e.g. in your controller or ApplicationController, etc., do the following:
rescue_from Stripe::CardError, with: :add_error_message_to_base
def add_error_message_to_base(e)
# this assumes that you set #instance in the controller's action method.
#instance.errors.add :base, e.message
respond_with #instance
end
or more generically:
rescue_from Stripe::CardError, with: :add_error_message_to_base
def add_error_message_to_base(e)
model_class_name = self.class.name.chomp('Controller').split('::').last.singularize
instance_value = instance_variable_get("##{model_class_name}")
instance_value.errors.add :base, e.message if instance_value
respond_with instance_value
end
or in a concern, you could do either of the above, putting the rescue_from into the included block:
module StripeErrorHandling
extend ::ActiveSupport::Concern
included do
rescue_from Stripe::CardError, with: :add_error_message_to_base
end
def add_error_message_to_base(e)
# see comment above...
#instance.errors.add :base, e.message
respond_with #instance
end
end
And you can use config.exceptions_app to handle errors at the Rack-level as José Valim describes here.
You could also inherit the method vs. having a separate service class, or have a concern/module. You might even do through hooks, e.g.:
# not exactly what you were doing but just for example.
# could put in app/controller/concerns among other places.
module ActionsCreateStripeCustomer
extend ::ActiveSupport::Concern
included do
around_action :create_stripe_customer
end
def create_stripe_customer
# this (indirectly) calls the action method, and you will
# set #instance in your action method for this example.
yield
customer = Stripe::Customer.find_or_create_by(description: 'Accommodation', email: object.email, card: token)
# could set customer on #instance here and save if needed, etc.
rescue Stripe::CardError => e
if #instance
#instance.errors.add :base, e.message
respond_with #instance
else
logger.warn("Expected #instance to be set by #{self.class.name}##{params[:action]}")
raise e
end
end
end
Then in the controller:
include ActionsCreateStripeCustomer
There is also before_action, after_action, etc. Also, you can just include modules and when instance methods are called they call on the including class instance first, then the first included module, then the second, etc. if you do super if defined?(super) to call the prior method, and it automatically puts in all the arguments and block.
And, if it were about getting the model class name rather than the instance, that is easy, too. Say the class you were calling from was AccountStripeCommunicator, then #model_class after the following would be Account:
qualified_class_name = self.class.name.chomp('StripeCommunictor')
#model_class = qualified_class_name.split('::').last.singularize.constantize
All kinds of possibilities.
For a specific role (group of users) I added the :readonly to every find on the active record
def self.find(*args)
if User.current_user.has_role? 'i_can_only_read'
with_scope({:find => {:readonly => true}}) do
result = super *args
end
end
end
Of course it raises now ActiveRecord::ReadOnlyRecord Exceptions in Controller passed on to the user; not very nice.
Can I catch this type of error in one place? Like in production.rb or in the application.rb? Or can I configure a specific error page for this error?
Yes, simply override rescue_action_in_public like this:
class ApplicationController < ActionController::Base
...
def rescue_action_in_public(exception)
case exception
when ActiveRecord::ReadOnlyRecord
# DO SOME LOGIC HERE
end
end
end
end
This will execute your action when in "production", but leave you with an informative stack trace when you are in "development".
Rails has a number of other rescue_action_* methods that might be more suitable to your problem...take a look at http://api.rubyonrails.org/classes/ActionController/Rescue.html