RSpec having trouble stubbing method called with inline rescue - ruby-on-rails

I'm trying test a method on a controller:
def a_method(list)
#users = []
list.each do |x|
if user=User.find(x) rescue nil
#users << user
end
end
end
In my Rspec example I have :
it "should do something" do
User.stub :find => 'user'
controller.a_method([1,2,3,4])
assigns[:users].should == ['user','user','user','user']
end
Problem:
it always rescues the find method user=User.find(x) rescue nil, even though I've stubbed it out.
If I remove the rescue nil it works fine.
Any ideas?

The if conditional doesn't accept a statement modifier such as rescue half way into the statement.
You can put the rescue at the end of the complete if statement as in:
if user=User.find(x)
#users << user
end rescue nil

why don't you use find_by_id instead of find?
find_by_id returns nil if the id does not exists instead of throwing the exception, it's almost the same you are doing but a little faster I guess and cleaner to read it

Related

Calling method_missing for undefined attributes in Rails after using "update" method

Is there a short way for obj.update(attr1: "something") method to call method_missing instead of raising the error ActiveModel::UnknownAttributeError (unknown attribute 'attr1' for Obj.)?
I am thinking about simply rescuing it and then mimicking/calling the method_missing, but this way feels too bulky.
From the source code (Rails 4.2) it seems that ActiveRecord::UnknownAttributeError is raised when the model instance does not respond_to? to the given attribute setter. So what you have to do is define a method_missing as well as respond_to_missing? in the model for all your dynamic attributes. This is actually what you always should do when using method_missing anyway:
class Model < ActiveRecord::Base
DYNAMIC_ATTRIBUTES = [:attr1, :attr2]
def method_missing(method_name, *arguments, &block)
if DYNAMIC_ATTRIBUTES.map { |attr| "#{attr}=" }.include?(method_name.to_s)
puts "custom code for #{method_name} #{arguments.first.inspect}"
else
super
end
end
def respond_to_missing?(method_name, include_private = false)
DYNAMIC_ATTRIBUTES.map { |attr| "#{attr}=" }.include?(method_name.to_s) || super
end
end
Test in Rails console:
Model.first.update(attr1: 'aa', attr2: 'bb')
# => custom code for attr1= "aa"
# => custom code for attr2= "bb"
Model.first.update(attr1: 'aa', attr2: 'bb', attr3: 'cc')
# => ActiveRecord::UnknownAttributeError: unknown attribute 'attr3' for Model.
Something like this?
rescue_from ActiveModel::UnknownAttributeError do |exception|
raise NoMethodError
# or however you want to hanle
end
You can try this:
begin
obj.update(attr1: "something")
rescue Exception => ex
if ex.class == ActiveRecord::UnknownAttributeError
method_missing
else
raise ex
end
end

Ruby: Skip element in loop if an exception is raised

I have the following method:
def fetch_something
#fetch_something ||= array_of_names.inject({}) do |results, name|
begin
results[name] = fetch_value!(name)
rescue NoMethodError, RuntimeError
next
end
results
end
end
To its purpose: It fetches a value for a given name that can raise an error, in which case it will ignore the name and try the next one.
While this works fine I get an error from Rubocop that says:
Lint/NextWithoutAccumulator: Use next with an accumulator argument in
a reduce.
Googling that error leads me to http://www.rubydoc.info/gems/rubocop/0.36.0/RuboCop/Cop/Lint/NextWithoutAccumulator where it says to not omit the accumulator, which would result in a method looking like this:
def fetch_something
#fetch_something ||= array_of_names.inject({}) do |results, name|
begin
results[name] = fetch_value!(name)
rescue NoMethodError, RuntimeError
next(name)
end
results
end
end
The problem is, that this change breaks the otherwise working method. Any ideas on how to tackle that?
Update: Demonstrational example:
array_of_names = ['name1','name2','name3']
def fetch_value!(name)
# some code that raises an error if the name doesn't correspond to anything
end
fetch_something
# => {'name1' => {key1: 'value1', ...}, 'name3' => {key3: 'value3', ...}}
# 'name2' is missing since it wasn't found durcing the lookup
Using your example code, it seems that next(results) does fix the issue for me. I've used some test code that throws a KeyError instead of NoMethodError or RuntimeError, but the idea is still the same:
#array_of_names = ['name1','name2','name3']
def fetch_value!(name)
{'name1' => 'n1', 'name3' => 'n3'}.fetch(name)
end
def fetch_something
#fetch_something ||= #array_of_names.inject({}) do |results, name|
begin
results[name] = fetch_value!(name)
rescue NoMethodError, RuntimeError, KeyError
next(results)
end
results
end
end
p fetch_something
This code outputs:
{"name1"=>"n1", "name3"=>"n3"}
Also, I agree with #Алексей Кузнецов that each_with_object is probably the way to go whenever your block code mutates the data structure you're trying to build. So my preferred implementation of fetch_something might be more like this:
def fetch_something
#fetch_something ||= #array_of_names.each_with_object({}) do |name, results|
begin
results[name] = fetch_value!(name)
rescue NoMethodError, RuntimeError, KeyError
# error handling
end
end
end
Note that in my example the begin/end block is outside the assignment to results[name] in contrast to #Алексей Кузнецов's example which will assign nil to the hash every time an exception occurs.
Just use each_with_object
def fetch_something
#fetch_something ||= array_of_names.each_with_object({}) do |name, results|
results[name] ||= begin
fetch_value!(name)
rescue NoMethodError, RuntimeError
end
end
end

How to return a value without `return`

How can I return without return like devise's authenticate! method does?
class GroupsController < ApplicationController
def create
authenticate! # After here, the code below will not be excuted.
#group = Group.create(group_params)
redirect_to groups_path
end
end
I am wondering how to do this.
The devise authenticate! doesn't return on failure, it actually throw exceptions if the user isn't authenticated. The exception will get propagated all through the call chain, until it hits a matched rescue statement. The Rails framework is smart enough that it will rescue this kind of exception and convert specific exceptions to the corresponding HTTP status code, for example, ActiveRecord::RecordNotFound will be converted to 404.
This is common programming tricks to return from deep call hierarchy.
def a
raise "ha"
end
def b
puts "calling a"
a
not executed
end
def c
b rescue nil
end
c #=> calling a
And ruby provides catch/throw which serve for this kind of deeper jump.
catch(:ret) do
(1..5).each do |i|
(1..5).each do |j|
puts i * j
throw :ret if i * j > 3
end
end
end
Are you just asking how to return without using the keyword 'return'?
Ruby will automatically return the result from the last line in the method, if thats what you mean. but it would be the same as using the keyword 'return'.

Handling an ActiveRecord error if database is empty

I'm working on a rails 4 app, and i have the following controller code
def index
#issue = Issue.find(1)
#sections = #issue.sections
#articles = #issue.articles
end
which breaks if the database is empty with the error: "Couldn't find Issue with id=1". What is the proper way to check for this in a way that if nothing is in the db it doesn't raise an error?
One method you can use is the exists? active record method, like so:
#issue = Issue.where(id: 1)
if #issue.exists?
# do something if it exists
else
# do something if it is missing
end
Side note: Since you're attempting to find by id, you don't necessarily need the .where portion; you can simply do: Issue.exists?(1).
exists? documentation on APIDoc
In most cases such exception is expected and recommenced. For example, you can rescue it with a custom 404 page.
Anyway, if you really don't want that, you can use find_by method which will output nil if nothing found
#issue = Issue.find_by(id: 1)
you can handle that exception in your controller
rescue_from ActiveRecord::RecordNotFound, :with => :record_not_found
def record_not_found
flash[:alert] = "invalid information"
redirect_to root_url
end
or you can use a where clause
#issue = Issue.where(id: 1).first
now check for nil by
#issue.nil?

How to Rescue From An Error in Rake

How do I rescue from a
undefined method
error in this code
for user in #users do
#customer = Stripe::Customer.retrieve(user.stripe_customer_token)
if #customer.subscription.nil?
elsif #customer.subscription.plan.id == 2
user.silver_reset
elsif #customer.subscription.plan.id == 3
user.gold_reset
end
end
I have tried a plain rescue call, but rake isn't liking it.
What is way to rescue from the error?
UPDATE:
The way I was doing it
for user in #users do
#customer = Stripe::Customer.retrieve(user.stripe_customer_token)
rescue_from Exception => exception
# Logic
end
if #customer.subscription.nil?
elsif #customer.subscription.plan.id == 2
user.silver_reset
elsif #customer.subscription.plan.id == 3
user.gold_reset
end
end
The Error
/home/user/rails_projects/assignitapp/lib/tasks/daily.rake:25: syntax error, unexpected keyword_rescue, expecting keyword_end
rescue Exception => exception
Rake 0.9.2.2
Rails 3.2.5
Use try to wrap the problem method and return nil if it doesn't exist. E.g.:
unless #customer = Stripe::Customer.try(:retrieve, user.stripe_customer_token)
# Logic
end
Alternatively, this catches more errors:
unless #customer = Stripe::Customer.retrieve(user.stripe_customer_token) rescue nil
# Logic
end
Or this is more what you were trying for:
#users.each do |user|
begin
#customer = Stripe::Customer.retrieve(user.stripe_customer_token)
rescue StandardError => error
# handle error
end
end
I still haven't enough reputation to comment, but regarding the above answer's third option: Don't rescue from Exception!
Exception is the root of Ruby's exception hierarchy, so when you rescue Exception you rescue from everything, including subclasses such as SyntaxError, LoadError, and Interrupt.
If you want to learn more, check out Why is it a bad style to `rescue Exception => e` in Ruby?

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