I would like load the particular record if it fails the validates_uniqueness constraint.
I have id (primary key) and title in my model. If the user enters a title which is already present if want to search for the record with the title and load that record instead of throwing the error.
Is there a way to do it?
You can use the before_validation callback to check validity yourself, and when it fails, trigger the behavior you're looking for. So, one way to do it would be to write code in before_validation, and in there you could do a simple .valid? call, or manually run the validation for uniqueness by itself. When validation fails, you can stop the callback chain, and trigger custom behavior.
before_validation is one of the many ActiveRecord callbacks available to you.
Another, more common way to do it would be, in your controller, instead of just saving you can basically wrap the .save call in an if statement, because .save returns false if validation fails. You can use this as a way to redirect to an alternate action, in the situation you describe.
#new_record = ThingImSaving.new(params[:thing_im_saving]
if #new_record.save
...validation has passed, continue the normal path
else
...validation has failed, do something else.
end
Related
I am not sure if I understand totally active record validation role.
Of course, if a user inputs data (like an email or a country), I can and should validate its existence, its uniqueness or its inclusion in a list of countries
But for example, if I have methods in the backend that change an attribute page_clicked or click_date or even the column update_at, that I "control" i.e 'is not generated by a user's input', should I use active record validations ?
I'm asking this because on a very 'hot database' (need speed for millions of frequent updates), I wonder if checking on each update that updated_at is a datetime, and that if a clicked column is true/false and nothing esle is really necessary as the user is not the one inputting/controlling these data but I am through Rails custom methods I wrote
Thanks
I don't think there is a general satisfying answer to your question. It's up to you to enforce validation or not.
Remember that you don't have to use ActiveRecord for validation, you can also use your DBMS to ensure that:
a value will never be NULL (one of the most annoying errors)
a value has the correct TYPE
a FOREIGN KEY always points to an existing row in another table
and depending on your DBMS, a lot more is possible
If you need high INSERT speed and want to go with raw SQL INSERTS, putting some validation in your database can prevent nasty application errors later.
Validations should guard your database and its job should be to stop saving the records that are considered invalid by your application.
There is no hard rule on what is valid record you have to decide it your self by adding the validations. If the record wont pass the validation step it is simply not going to be saved to the database.
From Active Record Callbacks:
3.1 Creating an Object
before_validation
after_validation
before_save
around_save
before_create
around_create
after_create
after_save
after_commit/after_rollback
3.2 Updating an Object
before_validation
after_validation
before_save
around_save
before_update
around_update
after_update
after_save
after_commit/after_rollback
You can see that validation hooks run at the beginning of the object life cycle.
So in your case instead of asking your self a question:
Should I use active record validations if the record is not generated by a user's input.
You should ask your self:
Is this record invalid without page_clicked or click_date(aka them being nil)
UPDATE
If you consider record to be invalid but worrying about speed problems with running validations I would do the validations to make sure that all the records in the database are valid and try to find the way to optimise the speed somewhere else. Plus not 100% sure but time spend on saving invalid records and filtering them later on will be probably much longer then validating in the first place.
When performance is really a priority and that I am sure that we developers / the server are the only ones who can manipulate specific attributes of a Model, I will
Make sure that I create a separate method / wrapper method for this specific action.
In this specific method, I call .save (validate: false) instead of the usual .save
I still write validations for the said attributes for developers' reference to prevent future development errors, and in case a new developer comes in and accidentally save an invalid record, precisely just because there's no validation to safeguard it.
Or, I will use .update_column instead of .save (validate: false) to perform a direct DB call, skipping Model validations and callbacks (If you also do not want callbacks to be called).
Note that .update_column is different from .update.
So a situation came up at work and I wanted to discuss it here because we could not get to an agreement between us:
We have two models, Order and Passport, which are related in a way that an Order has_one passport and a passport has_many orders. Whenever an order is completed, its associated passport must be 'locked', that is, turned into read-only (that information was already used to clear customs, so it can't be changed afterwards). We want to enforce that rule in the Passport model and we've thought of the following options:
Creating a validation. CONS: There will be records yielding valid? => false when technically the record is fine (although it can't be saved). For example, if other records have a validates_associated :passport on them, that could be a problem.
Overriding the readonly? method. CONS: This will raise an exception when trying to update that record, although you would expect that calling a save method won't ever raise one.
Creating a before_save callback. This has two flavors: either raise an exception (which is pretty much like the readonly? option) or add an #error and return false to stop the callback chain. CONS: Adding validation errors from outside a proper validation can be considered a bad practice. Also, you might find yourself calling valid? and getting true and then call save and get false.
This situation made us think a lot about the relationship between validations and Rails. What exactly does it mean for a record to be valid?? Does it imply that the save will work?
I would like to listen to your opinions to learn about this scenario. Maybe the best approach is neither one of the three! Thanks!
What about marking this record as read-only by using readonly! instance method? See the API
You could do it in a constructor, like:
class Passport < ActiveRecord::Base
def initialize(*args)
super(*args)
readonly! if orders.count>0 # or similar
end
end
I think there is an extra alternative. What you describe dictates that the Passport model can have some different states. I would consider using a state machine to describe the relevant orders status for the passport.
eg:
open
pending
locked
other_update_actions ...
With that in mind, all relevant order actions will trigger an event to the passport model and its state.
If it is possible to integrate the update actions to certain events then you could handle the readonly part in a more elegant way (incompatible state transition).
As an extra check you can always keep an ugly validator as a last resort to prevent the model from being updated without the state machine.
you can check the aasm gem for this
I have a User and a StripeCustomer model. Every User embeds one and accepts_nested_attributes_for StripeCustomer.
When creating a new user, I always create a corresponding StripeCustomer and if you provide either a CC or a coupon code, I create a subscription.
In my StripeCustomer:
attr_accessible :coupon_id, :stripe_card_token
What I'd like to do is, if the coupon is invalid, do:
errors.add :coupon_id, "bad coupon id"
So that normal rails controller patters like:
if #stripe_customer.save
....
else
....
end
will just work. And be able to use normal rails field_with_errors stuff for handling a bad coupon.
So the question is, at which active record callback should I call Stripe::Customer.create and save the stripe_customer_token?
I had it on before_create, because I want it done only if you are really going to persist the record. But this does strange things with valid? and worse, if you are going to create it via a User, the save of User and StripeCustomer actually succeeds even if you do errors.add in the before_create callback! I think the issue is that the save will only fail if you add errors and return false at before_validation.
That last part I'm not sure if it is a mongoid issue or not.
I could move it to before_validation :on => :create but then it would create a new Stripe::Customer even if I just called valid? which I don't want.
Anyway, I'm generically curious about what the best practices are with any model that is backed by or linked to a record on a remote service and how to handle errors.
Ok here is what I did, I split the calls to stripe into 2 callbacks, one at before_validation and one before_create (or before_update).
In the before_validation, I do whatever I can to check the uncontrolled inputs (directly from user) are valid. In the stripe case that just means the coupon code so I check with stripe that it is valid and add errors to :coupon_code as needed.
Actually creating/updating customers with stripe, I wait to do until before_create/before_update (I use two instead of just doing before_save because I handle these two cases differently). If there is an error then, I just don't handle the exception instead of trying to add to errors after validation which (a) doesn't really make any sense and (b) sort of works but fails to prevent saves on nested models (in mongoid anyway, which is very bad and strange).
This way I know by the time I get to persisting, that all the attributes are sound. Something could of course still fail but I've minimized my risk substantially. Now I can also do things like call valid? without worrying about creating records with stripe I didn't want.
In retrospect this seems pretty obvious.
I'm not sure I totally understand the scenario. you wrote:
Every User embeds one and accepts_nested_attributes_for StripeUser
Did you mean StripeCustomer?
So you have a User that has a Customer that holds the coupon info?
If so, I think it should be enough to accept nested attributed for the customer in the user, put the validation in the customer code and that's it.
See here
Let me know if I got your question wrong...
I was using before_validation, to do a few updates to the models before they are being validated and later on - saved.
Apparently, the validation callbacks aren't called when you save without validation.
What callback should I use to make sure this code runs before the save and before validation if it exists?
Skipping validation sounds like a workaround. You're better off calling validations conditionally if there are cases when you don't want to validate. That way it's testable as well.
This seems pretty hacky but...
def save
do_something
super
end
I'm using mongoid, and I want to migrate my documents one at a time. To do this, I've tried doing the migration in an after_initialize callback, but I can't seem to save() from there without triggering the same validation and infinite recursion. Is there a better callback to use, or a different thing I should be looking at?
Have you tried passing :validate => false into the save? That allows you to bypass validations.
As per the original question,
instance.update_attributes(new_attr_hash)
will immediately save after updating the instance, but you can't bypass validations with update_attributes.
I'd use before_save, and then go through the whole collection and save them again outside the callback, instead of just initializing them like I assume you were doing before.