I'm not sure this is even possible, but let's see if one of you comes up with a solution. This is more or less about code quality in terms of readability and not an actual problem because I already have a solution. I have a friendship model and a user model. The friendship model is used to model friendships between two users:
class Friendship
def self.requested(user)
where(:user_id => user).where(:status => 'requested')
end
def self.pending(user)
where(:user_id => user).where(:status => 'pending')
end
def self.accepted(user)
where(:user_id => user).where(:status => 'accepted')
end
# ...
end
class User
has_many :friendships
# ...
end
Is it somehow possible to call the requested, pending or accepted scope through
the user model without providing an argument?
a_user.friendships.pending # this does not work, is there a way to get it working?
a_user.friendships.pending(a_user) # works of course!
I think this should work if you take the argument off. Calling pending off of the user object like this should already scope friendships to the appropriate user. Define the method like this:
def self.pending
where(:status => 'pending')
end
And call:
a_user.friendships.pending
Check the logs for the generated query if you're not sure it's working.
If you still want to call it by passing an argument I'd name that method Friendship.pending_for(user).
Related
I'm working on a project to recreate some of the functionality of ActiveRecord. Here's the portion that isn't working
module Associations
def belongs_to(name, params)
self.class.send(:define_method, :other_class) do |name, params|
(params[:class_name] || name.camelize).constantize
end
self.class.send(:define_method, :other_table_name) do |other_class|
other_class.table_name
end
.
.
.
o_c = other_class(name, params)
#puts this and other (working) values in a query
query = <<-SQL
...
SQL
#sends it off with db.execute(query)...
I'm building towards this testing file:
require 'all_files' #holds SQLClass & others
pets_db_file_name = File.expand_path(File.join(File.dirname(__FILE__), "pets.db"))
DBConnection.open(pets_db_file_name)
#class Person
#end
class Pet < SQLClass
set_table_name("pets")
set_attrs(:id, :name, :owner_id)
belongs_to :person, :class_name => "Person", :primary_key => :id, :foreign_key => :owner_id
end
class Person < SQLClass
set_table_name("people")
set_attrs(:id, :name)
has_many :pets, :foreign_key => :owner_id
end
.
.
.
Without any changes I received
.../active_support/inflector/methods.rb:230:in `block in constantize': uninitialized constant Person (NameError)
Just to make sure that it was an issue with the order of loading the classes in the file I began the file with the empty Person class, which, as predicted gave me
undefined method `table_name' for Person:Class (NoMethodError)
Since this is a learning project I don't want to change the test to make my code work (open all the classes, set all the tables/attributes then reopen them them for belongs_to. But, I'm stuck on how else to proceed.)
EDIT SQLClass:
class SQLClass < AssignmentClass
extend SearchMod
extend Associations
def self.set_table_name(table_name)
#table_name = table_name
end
def self.table_name
#table_name
end
#some more methods for finding rows, and creating new rows in existing tables
And the relevant part of AssignmentClass uses send on attr_accessor to give functionality to set_attrs and makes sure that before you initialize a new instance of a class all the names match what was set using set_attrs.
This highlights an important difference between dynamic, interpreted Ruby (et al) and static, compiled languages like Java/C#/C++. In Java, the compiler runs over all your source files, finds all the class/method definitions, and matches them up with usages. Ruby doesn't work like this -- a class "comes into existence" after executing its class block. Before that, the Ruby interpreter doesn't know anything about it.
In your test file, you define Pet first. Within the definition of Pet, you have belongs_to :person. belongs_to does :person.constantize, attempting to get the class object for Person. But Person doesn't exist yet! Its definition comes later in the test file.
There are a couple ways I can think that you could try to resolve this:
One would be to do what Rails does: define each class in its own file, and make the file names conform to some convention. Override constant_missing, and make it automatically load the file which defines the missing class. This will make load order problems resolve themselves automatically.
Another solution would be to make belongs_to lazy. Rather than looking up the Person class object immediately, it could just record the fact that there is an association between Pet and Person. When someone tries to call pet.person, use a missing_method hook to actually define the method. (Presumably, by that time all the class definitions will have been executed.)
Another way would be do something like:
define_method(belongs_to) do
belongs_to_class = belongs_to.constantize
self.class.send(:define_method, belongs_to) do
# put actual definition here
end
self.send(belongs_to)
end
This code is not tested, it's just to give you an idea! Though it's a pretty mind-bending idea, perhaps. Basically, you define a method which redefines itself the first time it is called. Just like using method_missing, this allows you to delay the class lookup until the first time the method is actually used.
If I can say one more thing: though you say you don't want to "overload" method_missing, I don't think that's as much of a problem as you think. It's just a matter of extracting code into helper methods to keep the definition of method_missing manageable. Maybe something like:
def method_missing(name,*a,&b)
if has_belongs_to_association?(name)
invoke_belongs_to_association(name,a,b)
elsif has_has_many_association?(name)
invoke_has_many_association(name,a,b)
# more...
else
super
end
end
Progress! Inspired by Alex D's suggestion to use method_missing to delay the creation I instead used define_methodto create a method for the name, like so:
define_method, :other_class) do |name, params|
(params[:class_name] || name.camelize).constantize
end
define_method(:other_table_name) do |other_class|
other_class.table_name
end
#etc
define_method(name) do #|params| turns out I didn't need to pass in `params` at all but:
#p "---#{params} (This is line 31: when testing this out I got the strangest error
#.rb:31:in `block in belongs_to': wrong number of arguments (0 for 1) (ArgumentError)
#if anyone can explain this I would be grateful.
#I had declared an #params class instance variable and a getter for it,
#but nothing that should make params require an argument
f_k = foreign_key(name, params)
p f_k
o_c = other_class(name, params)
o_t_n = other_table_name(o_c)
p_k = primary_key(params)
query = <<-SQL
SELECT *
FROM #{o_t_n}
WHERE #{p_k} = ?
SQL
row = DBConnection.execute(query, self.send(f_k))
o_c.parse_all(row)
end
Say I am keeping track of email correspondances. An enquiry (from a customer) or a reply (from a supporter) is embedded in the order the two parties are corresponding about. They share the exact same logic when put into the database.
My problem is that even though I use the same logic, the object classes are different, the model fields I need to call are different, and the method names are different as well.
How do I put methods and objects references in before I actually have to use them? Does a "string_to_method" method exists or something like that?
Sample code with commentaries:
class Email
include Mongoid::Document
field :from, type: String
field :to, type: String
field :subject, type: String
belongs_to :order, :inverse_of => :emails
def start
email = Email.create!(:from => "sender#example.com", :to => "recipient#example.com", :subject => "Hello")
from_or_to = from # This represents the database field from where I later on will fetch the customers email address. It is either from or to.
enquiries_or_replies = enquiries # This represents a method that should later be called. It is either enquiries or replies.
self.test_if_enquiry_or_reply(from_or_to, enquiries_or_replies)
end
def test_if_enquiry_or_reply(from_or_to, enquiries_or_replies)
order = Order.add_enquiry_or_reply(self, from_or_to, enquiries_or_replies)
self.order = order
self.save
end
end
class Order
include Mongoid::Document
field :email_address, type: String
has_many :emails, :inverse_of => :order
embeds_many :enquiries, :inverse_of => :order
embeds_many :replies, :inverse_of => :order
def self.add_enquiry_or_reply(email, from_or_to, enquiries_or_replies)
order = Order.where(:email_address => email.from_or_to).first # from_or_to could either be from or to.
order.enquiries_or_replies.create!(subject: email.subject) # enquiries_or_replies could either be enquiries or replies.
order
end
end
Judging by the question and the code sample, it sounds like you are mixing concerns too much. My first suggestion would be to re-evaluate your method names and object structure. Ambiguous names like test_if_thing1_or_thing2 and from_or_to (it should just be one thing) will make it very hard for others, and your future self, to understand the code laster.
However, without diverging into a debate on separation of concerns, you can change the methods you call by using public_send (or the private aware send). So you can do
order.public_send(:replies).create!
order.public_send(:enquiries).create!
string to method does exist, it's called eval
so, you could do
method_name = "name"
eval(method_name) #calls the name method
having this code block of an example rails model class:
class Block < ActiveRecord::Base
has_many :bricks, :autosave => true
def crunch
bricks.each do |brick|
if brick.some_condition?
brick.name = 'New data'
brick.save # why do I have to call this?
end
end
end
end
class Brick < ActiveRecord::Base
belongs_to :block, :autosave => true
end
I found that the only way to make sure the changes within the associated objects get saved for me, was to call brick.save manually. Even thought I use :autosave => true
Why?
Probably the autosave option has a misleading name. By the way, it's the expected behaviour. The option is meant for association. So if you modify an object in a relation and save the other object then ActiveRecord saves the modified objects. So, in your case, you could change your code to:
def crunch
bricks.each do |brick|
if brick.some_condition?
brick.name = 'New data'
end
end
save # saving the father with autosave should save the children
end
You could use any of the helper methods available: update_attribute, update_attributes, update_column...
More info: Rails: update_attribute vs update_attributes
I have a simple user model
class User < ActiveRecord::Base
has_one :user_profile
end
And a simple user_profile model
class UserProfile < ActiveRecord::Base
belongs_to :user
end
The issue is when I call the following build method, without calling the save method, I end up with a new record in the database (if it passes validation)
class UserProfilesController < ApplicationController
def create
#current_user = login_from_session
#user_profile = current_user.build_user_profile(params[:user_profile])
##user_profile.save (even with this line commented out, it still save a new db record)
redirect_to new_user_profile_path
end
Anyyyyyy one have anyyy idea what's going on.
The definition of this method says the following but it's still saving for me
build_association(attributes = {})
Returns a new object of the associated type that has been instantiated with attributes and linked to this object through a foreign key, but has not yet been saved.
http://api.rubyonrails.org/classes/ActiveRecord/Associations/ClassMethods.html#method-i-has_one
Ok, I'm sure experienced vets already know this, but as a rookie I had to figure it out the long way...let me see if I can explain this without screwing it up
Although I was not directly saving the user_profile object, I noticed in my logs that something was updating the user model's last_activity_time (and the user_profile model) each time I submitted the form (the user model's last_activity date was also updated when the logged in user did various other things too - I later realized this was set in the Sorcery gem configuration).
Per http://api.rubyonrails.org/classes/ActiveRecord/AutosaveAssociation.html
AutosaveAssociation is a module that takes care of automatically saving associated records when their parent is saved. In my case, the user mode is the parent and the scenario they provide below mirrors my experience.
class Post
has_one :author, :autosave => true
end
post = Post.find(1)
post.title # => "The current global position of migrating ducks"
post.author.name # => "alloy"
post.title = "On the migration of ducks"
post.author.name = "Eloy Duran"
post.save
post.reload
post.title # => "On the migration of ducks"
post.author.name # => "Eloy Duran"
The following resolutions resolved my problem
1. Stopping Sorcery (config setting) from updating the users last_activity_time (for every action)
or
2. Passing an ':autosave => false' option when I set the association in the user model as follows
class User < ActiveRecord::Base
has_one :user_profile, :autosave => false
end
I have this:
def valid_attributes
{ :email => "some_#{rand(9999)}#thing.com" }
end
For Rspec testing right? But I would like to do something like this:
def valid_attributes
static user_id = 0
user_id += 1
{ :email => "some_#{user_id}#thing.com" }
end
I don't want user_id to be accessible from anywhere but that method,
is this possible with Ruby?
This is a closure case. Try this
lambda {
user_id = 0
self.class.send(:define_method, :valid_attributes) do
user_id += 1
{ :email => "some_#{user_id}#thing.com" }
end
}.call
Wrapping everything in lambda allows the variables defined within lambda to only exist in the scope. You can add other methods also. Good luck!
This answer is a little larger in scope than your question, but I think it gets at the root of what you're trying to do, and will be the easiest and most maintainable.
I think what you're really looking for here is factories. Try using something like factory_girl, which will make a lot of testing much easier.
First, you'd set up a factory to create whatever type of object it is you're testing, and use a sequence for the email attribute:
FactoryGirl.define do
factory :model do
sequence(:email) {|n| "person#{n}#example.com" }
# include whatever else is required to make your model valid
end
end
Then, when you need valid attributes, you can use
Factory.attributes_for(:model)
You can also use Factory.create and Factory.build to create saved and unsaved instances of the model.
There's explanation of a lot more of the features in the getting started document, as well as instructions on how to add factories to your project.
You can use a closure:
def validator_factory
user_id = 0
lambda do
user_id += 1
{ :email => "some_#{user_id}#thing.com" }
end
end
valid_attributes = validator_factory
valid_attributes.call #=> {:email=>"some_1#thing.com"}
valid_attributes.call #=> {:email=>"some_2#thing.com"}
This way user_id won't be accessible outside.
I'd use an instance variable:
def valid_attributes
#user_id ||= 0
#user_id += 1
{ :email => "some_#{#user_id}#thing.com" }
end
The only variables Ruby has are local variables, instance variables, class variables and global variables. None of them fit what you're after.
What you probably need is a singleton that stores the user_id, and gives you a new ID number each time. Otherwise, your code won't be thread-safe.