I'm in the process of creating a product configurator. Trouble is that each product has many components, which are themselves configurable. Imagine you're configuring a computer when buying it.
The dependencies sometimes apply when a component is selected, or when a quantity of a component, or even a combination of both. It all becomes very complicated at some point, and is not consistent across products, as each is its own universe in a sense.
Oh, and these rules change all the time, so coding them in the app is not really an option for me.
I was hoping to be able to store the code of a method called validate in the database.
Each configuration would have it's own version of validate, which would be stored as a text in the db, and could be changed if/when required.
Is is possible to do this? How can i take text and have rails actually execute whatever this text says?
For example i have this:
irb(main):246:0> #h= Configuration.find(1).rule
=> "def getmax3(inputarray)\n #maxpos = 0\n inputarray.each do |h|\n if #maxpos < h.position\n #maxpos = h.position\n end\n end\n 1\n end"
which obviosly isn't code. The method above is of course just a test as I'm trying to figure things out.
(Oh and I know it must be horrible practice to do this, but I really can't think of another way)
Thanks a lot!
Yes it is an horrible practice :)
If you had simple and stabilized rules to implement, you could store some variables in a dedicated table and use those variables in your rules; since it looks like you don't really know what is going to happen about those rules, be ready to accept any challenge by using a tested and proven workflow.
Here's my suggestion:
Setup an automatic deploy procedure using capistrano and other tools
Write your rules in a dedicated validation library
Code & test rules, commit and deploy
Defining a DSL can make your life easier, if you are committed in the long term to manipulate such rules and you could not be the only one in charge of such task; observe how the rules are changed over a good amount of time and you will know if having a dedicated DSL is a good thing or a waste of time.
I might be misunderstanding your problem, but if you could get that code out of the database and into files that can be tested and versioned, you'll be in a much happier place. Without knowing the intricacies of your models, it's hard to say what the best approach would be, but I guarantee one is out there.
I've used Single Table Inheritance in the past for modeling complex systems that have related components which share common properties and behavior. You might be able to use this approach with your application. STI basically says you have a parent class, in your case Configuration, and subclasses, that all reside in the same table. If there is shared behavior among some but not all of the subclasses, then you can move that code to modules and include in the classes that need it.
Basic parent class would just inherit from ActiveRecord:
class Configuration < ActiveRecord::Base
end
Then each subclass would have its logic defined within it:
class Component < Configuration
def getmax3(inputarray)
#maxpos = 0
inputarray.each do |h|
if #maxpos < h.position
#maxpos = h.position
end
end
1
end
end
I'm not saying this is the direction you want to go, but hopefully it will make you think about other ways of modeling your system.
Related
TL;DR: I don't know how organise my logic domain classes.
I have the model "Application", this model is in the "core" of the App and is the way I "enter" and operate over other models like:
#application = Application.find(params[:application_id])
#application.payment.update_attribute 'active', true
or
unless #application.report.status
or
#application.set_income(params[:income][:new_income])
so the models Payment, Income and Report are basically empty because I initialise the Application model and from there I do things "on cascade" to change the "subordinated" models. But now the Application model has more than forty methods and 600 lines.
I'm doing it right? For instance when I want to add a new Payment I like to do :
payment = Payment.create params
inside the Application model because ActiveRecord "knows" how to handle the foreign keys automatically. I could create the payment inside the Payment model using:
application = Application.find(application_id)
params[:application_id] = application.id
self.create params
but this way, I need to set the Application.id manually and that looks more verbose and not elegant.
So --if I want to reduce my Application model--, should I create modules in APP/lib directory or should I move methods to the other models?
should I create modules in APP/lib directory
Basically, yes, that's what you should do. Although I'd probably make them classes rather than modules. The pattern it sounds like you're after is called "service Objects" (or sometimes "use cases"). What this does is takes the logic from a specific operation you want to perform, and puts it in it's own self-contained class. That class then collaborates with whatever models it needs to. So, your models stay quite small, and your "Service Classes" follow the Single Responsibility Principle. Your controllers then usually call a single "service class" to do what they need to do - so your controllers stay pretty minimal too.
If you google "rails service objects" or similar, you'll find lots of great stuff, but here's some resources to get you started.
Service objects rails casts: https://www.youtube.com/watch?v=uIp6N89PH-c
https://webuild.envato.com/blog/a-case-for-use-cases/
https://blog.engineyard.com/2014/keeping-your-rails-controllers-dry-with-services
http://blog.codeclimate.com/blog/2012/10/17/7-ways-to-decompose-fat-activerecord-models/ (there's one section on service objects there)
Keep in mind, once you do start using service objects, you don't necessarily have to ALWAYS go through your Application model to get to the related ones. A service object might take an application_id and then do eg. #payment = Payment.find_by(application_id: application_id) and so you don't have to fetch the application instance at all and can manipulate the #payment variable directly.
The fact that Rails makes it "easy" and "pretty" to get to related models doesn't necessarily mean you should do it.
I would not worry about long controller and spec files in Rails.
These files tend to get very long and the usual advice of keeping classes and methods short does not necessarily apply for controllers and their specs.
For example, in our production system user_controller.rb is 8500 lines long and the corresponding user_controller_spec.rb is 7000 lines long.
This is the length of our top 10 controllers
1285 app/controllers/*********_controller.rb
1430 app/controllers/***********_controller.rb
1444 app/controllers/****_controller.rb
1950 app/controllers/****_controller.rb
1994 app/controllers/********_controller.rb
2530 app/controllers/***********_controller.rb
2697 app/controllers/*********_controller.rb
2998 app/controllers/*****_controller.rb
3134 app/controllers/application_controller.rb
8737 app/controllers/users_controller.rb
TL;DR: If your app has four models that are all tied to tables in your database (ie. leveraging ActiveRecord and inheriting from ActiveModel::Base), the framework is pretty opinionated toward using model classes.
Abstractions of the service class pattern can be useful in some cases, but give yourself a break. One of the advantages of Rails is that its supposed to remove a lot of the barriers to development, among many things, by making organization decisions for you. Leverage your model classes.
Let's see if this starts an epic developer bickering war.
Also, its ok to create interfaces in your models for related model creation:
class Application < ActiveModel::Base
has_one :payment
def create_payment(attrs)
payment.create(attrs)
end
end
And by ok, i mean that the framework will allow this. But remember, you're already inheriting from ActiveModel::Base which defines many instance methods, including create.
I would recommend, esp. if this is a small project and you're just getting your feet wet, to use well-named rails controllers to read and write objects to the database:
class ApplicationPaymentsController < ActionController::Base
def create
application = Application.find(params[:id])
application.create_payment(payment_params)
end
private
def payment_params
params.require(:payment).permit(:x, :y) - whatever your attr names are.
end
end
The sleekness you're looking for in abstracting foreign keys in creating a relational record is taken care of for you with Rails associations:
http://guides.rubyonrails.org/association_basics.html (good starting point)
http://apidock.com/rails/ActiveRecord/Associations/ClassMethods/has_one (more explicit docs)
That will help you slim down models if that is your goal. Just for clarification, this is one of those things that devs are extremely opinionated on, one way or another, but the truth is that there are code smells (which should be addressed) and then there are folks who arbitrary preach file length maxes. The most important thing in all of this is readable code.
A good litmus test for refactoring working code is put it down for a few weeks, come back to it, and if its confusing then put in some time to make it better (hopefully guided by already written test coverage). Otherwise, enjoy what you do, especially if you're working solo.
I am only looking for answers from senior/more experienced Ruby/Rails developers on this one, since I think this is a bit more advanced of a question.
I have a gem I am working on that adds some behavior to AR models. I have to test it for a lot of different associations (has_many, habtm, has_one etc), and I also have to test behavior when different options are passed for the associations (e.g. :foreign_key). Now with all these different models, I can use the same table in the database because the fields themselves do not need to change, only behavior specified through has_many, belongs_to and so on.
Keep in mind there are a lot of different options, so the number of models is quite large.
First I don't think it would be bad practice to have the definition of the models next to / in the test itself, for readability purposes (if I have multiple tests that use the same model then I would group them together and use the before method). So this is one of my goals, and you can comment on this if you don't agree.
The second thing I am not sure of is I wanted to keep the simple/same name of the model in all the tests, for example "Task", instead of TaskWithManySubtasksAndForeignKey or something ugly like that. The problem is there are so many models it's hard to come up with meaningful and simple names. I'm not quite sure about this - using the same name, since it's a constant, is a little problematic. I have a solution with a proxy class but I don't think this is the optimal solution. I was considering using variables (with the let method) like "taskModel", but it seemed a little verbose and unusual.
One other option that comes to mind, but I am not sure is possible to do easily, is to remove an existing association and then define a new one. So e.g. add a has_many and then remove it, add a habtm...
How would you go about doing this?
Defining unique models in the spec files is not necessarily a bad idea since it makes it easy to see exactly how each model is defined. The obvious problem with this approach is if you want to reuse the models in other test files. The Rails approach to this is to define all the models in separate files and then just require them in the tests that need it.
I think it really just depends on how many models you have and how much you want to reuse. In one of my gems, I took the approach of defining the models in the spec file, in another gem, I defined them in the spec helper, and in yet another I took the Rails approach and used a separate directory for them. If you asked me which one I preferred, I'd probably go with the spec that also contains the models because it's all in one place. Definitely a subjective problem though.
Another approach I've taken on occasion is to create an anonymous class that's guaranteed to only be around for the life of that test:
describe 'my test' do
let(:my_class) do
Class.new(Task) do
has_many :things
belongs_to :something_else
end
end
it 'should have many things' do
my_class.should have(100).things
end
end
I am looking for a Ruby/Rails tool that will help me accomplish the following:
I would like to store the following string, and ones similar to it, in my database. When an object is created, updated, deleted, etc., I want to run through all the strings, check to see if the CRUD event matches the conditions of the string, and if so, run the actions specified.
When a new ticket is created and it's category=6 then notify user 1234 via email
I am planning to create an interface that builds these strings, so it doesn't need to be a human-readable string. If a JSONish structure is better, or a tool has an existing language, that would be fantastic. I'm kinda thinking something along the lines of:
{
object_types: ['ticket'],
events: ['created', 'updated'],
conditions:'ticket.category=6',
actions: 'notify user',
parameters: {
user:1234,
type:'email'
}
}
So basically, I need the following:
Monitor CRUD events - It would be nice if the tool had a way to do this, but Ican use Rails' ModelObservers here if the tool doesn't natively provide it
Find all matching "rules" - This is my major unknown...
Execute the requested method/parameters - Ideally, this would be defined in my Ruby code as classes/methods
Are there any existing tools that I should investigate?
Edit:
Thanks for the responses so far guys! I really appreciate you pointing me down the right paths.
The use case here is that we have many different clients, with many different business rules. For the rules that apply to all clients, I can easily create those in code (using something like Ruleby), but for all of the client-specific ones, I'd like to store them in the database. Ideally, the rule could be written once, stored either in the code, or in the DB, and then run (using something Resque for performance).
At this point, it looks like I'm going to have to roll my own, so any thoughts as to the best way to do that, or any tools I should investigate, would be greatly appreciated.
Thanks again!
I don't think it would be a major thing to write something yourself to do this, I don't know of any gems which would do this (but it would be good if someone wrote one!)
I would tackle the project in the following way, the way I am thinking is that you don't want to do the rule matching at the point the user saves as it may take a while and could interrupt the user experience and/or slow up the server, so...
Use observers to store a record each time a CRUD event happens, or to make things simpler use the Acts as Audited gem which does this for you.
1.5. Use a rake task, running from your crontab to run through the latest changes, perhaps every minute, or you could use Resque which does a good job of handling lots of jobs
Create a set of tables which define the possible rules a user could select from, perhaps something like
Table: Rule
Name
ForEvent (eg. CRUD)
TableInQuestion
FieldOneName
FieldOneCondition etc.
MethodToExecute
You can use a bit of metaprogramming to execute your method and since your method knows your table name and record id then this can be picked up.
Additional Notes
The best way to get going with this is to start simple then work upwards. To get the simple version working first I'd do the following ...
Install acts as audited
Add an additional field to the created audit table, :when_processed
Create yourself a module in your /lib folder called something like processrules which roughly does this
3.1 Grabs all unprocessed audit entries
3.2 Marks them as processed (perhaps make another small audit table at this point to record events happening)
Now create a rules table which simply has a name and condition statement, perhaps add a few sample ones to get going
Name: First | Rule Statement: 'SELECT 1 WHERE table.value = something'
Adapt your new processrules method to execute that sql for each changed entry (perhaps you want to restrict it to just the tables you are working with)
If the rule matched, add it to your log file.
From here you can extrapolate out the additional functionality you need and perhaps ask another question about the metaprogramaming side of dynamically calling methods as this question is quite broad, am more than happy to help further.
I tend to think the best way to go about task processing is to setup the process nicely first so it will work with any server load and situation then plug in the custom bits.
You could make this abstract enough so that you can specify arbitrary conditions and rules, but then you'd be developing a framework/engine as opposed to solving the specific problems of your app.
There's a good chance that using ActiveRecord::Observer will solve your needs, since you can hardcode all the different types of conditions you expect, and then only put the unknowns in the database. For example, say you know that you'll have people watching categories, then create an association like category_watchers, and use the following Observer:
class TicketObserver < ActiveRecord::Observer
# observe :ticket # not needed here, since it's inferred by the class name
def after_create(ticket)
ticket.category.watchers.each{ |user| notify_user(ticket, user) }
end
# def after_update ... (similar)
private
def notify_user(ticket, user)
# lookup the user's stored email preferences
# send an email if appropriate
end
end
If you want to store the email preference along with the fact that the user is watching the category, then use a join model with a flag indicating that.
If you then want to abstract it a step further, I'd suggest using something like treetop to generate the observers themselves, but I'm not convinced that this adds more value than abstracting similar observers in code.
There's a Ruby & Rules Engines SO post that might have some info that you might find useful. There's another Ruby-based rules engine that you may want to explore that as well - Ruleby.
Hope that this helps you start your investigation.
thanks for your time first...after all the searching on google, github and here, and got more confused about the big words(partition/shard/fedorate)，I figure that I have to describe the specific problem I met and ask around.
My company's databases deals with massive users and orders, so we split databases and tables in various ways, some are described below:
way database and table name shard by (maybe it's should be called partitioned by?)
YZ.X db_YZ.tb_X order serial number last three digits
YYYYMMDD. db_YYYYMMDD.tb date
YYYYMM.DD db_YYYYMM.tb_ DD date too
The basic concept is that databases and tables are seperated acording to a field(not nessissarily the primary key), and there are too many databases and too many tables, so that writing or magically generate one database.yml config for each database and one model for each table isn't possible or at least not the best solution.
I looked into drnic's magic solutions, and datafabric, and even the source code of active record, maybe I could use ERB to generate database.yml and do database connection in around filter, and maybe I could use named_scope to dynamically decide the table name for find, but update/create opertions are bounded to "self.class.quoted_table_name" so that I couldn't easily get my problem solved. And even I could generate one model for each table, because its amount is up to 30 most.
But this is just not DRY!
What I need is a clean solution like the following DSL:
class Order < ActiveRecord::Base
shard_by :order_serialno do |key|
[get_db_config_by(key), #because some or all of the databaes might share the same machine in a regular way or can be configed by a hash of regex, and it can also be a const
get_db_name_by(key),
get_tb_name_by(key),
]
end
end
Can anybody enlight me? Any help would be greatly appreciated~~~~
Case two (where only db name changes) is pretty easy to implement with DbCharmer. You need to create your own sharding method in DbCharmer, that would return a connection parameters hash based on the key.
Other two cases are not supported right away, but could be easily added to your system:
You implement sharding method that knows how to deal with database names in your sharded dabatase, this would give you an ability to do shard_for(key) calls to your model to switch db connection.
You add a method like this:
class MyModel < ActiveRecord::Base
db_magic :sharded => { :sharded_connection => :my_sharding_method }
def switch_shard(key)
set_table_name(table_for_key(key)) # switch table
shard_for(key) # switch connection
end
end
Now you could use your model like this:
MyModel.switch_shard(key).first
MyModel.switch_shard(key).count
and, considering you have shard_for(key) call results returned from the switch_shard method, you could use it like this:
m = MyModel.switch_shard(key) # Switch connection and get a connection proxy
m.first # Call any AR methods on the proxy
m.count
If you want that particular DSL, or something that matches the logic behind the legacy sharding you are going to need to dig into ActiveRecord and write a gem to give you that kind of capability. All the existing solutions that you mention were not necessarily written with your situation in mind. You may be able to bend any number of solutions to your will, but in the end you're gonna have to probably write custom code to get what you are looking for.
Sounds like, in this case, you should consider not use SQL.
If the data sets are that big and can be expressed as key/value pairs (with a little de-normalization), you should look into couchDB or other noSQL solutions.
These solutions are fast, fully scalable, and is REST based, so it is easy to grow and backup and replicate.
We all have gotten into solving all our problems with the same tool (Believe me, I try to too).
It would be much easier to switch to a noSQL solution then to rewrite activeRecord.
I have a rails app moving along fairly well, but the fact that I'm doing this myself means that some poor sod is eventually going to see this and say, "What the hell were you thinking? Why did you put this here?!?!"
Where is that poor, sorry soul going to expect to see a series of classes that aren't used by anything but a single model class? Obviously, I could chuck it in the_model.rb along with class TheModel, but this may expand beyond the planned two classes...
I thought about lib, but it doesn't need to clutter everyone's view of the world....
Thank you.
My predecessor thanks you.
Leave them in the_model.rb until you need them in more than one place. If you refactor needlessly, you're not doing the simplest thing that could possibly work. You aren't gonna need it.
At that point, the general pattern is to create a directory for "concerns". See this weblog post by Jamis Buck or this one by Peter Marklund for more information.
In general: follow the Rails naming conventions when translating class names into filesystem locations. (that is: keep the class FooHelper::Bar in foo_helper/bar.rb)
You can make exceptions for small helper classes that are only used once and keep them in the same file as your model, but those should be exceptions. (but the converse is also true, don't create one-line thousands of single line files)
Use modules and class namespaces to your advantage. If you have a helper class that is only used by (and dependent on) your model, put them into the namespace of the model class:
class TheModel::HelperClass
end
the location in the file system would be app/models/the_model/helper_class.rb
And something that is not dependent on your model can probably still be namespaced
module Bar
class Foo
end
end
living in bar/foo.rb, of course
You should probably not be afraid to put things that are not models into lib -- that's what this directory is for
I'd say concerns, while useful, are not really the right way to go because that is a way to split a single class into multiple files and you don't seem to be doing that.