type check for a field in table (postgres) rails

Question

I have a table Student(class_id(integer),marks(integer),rank(integer))

In my Seeds.rb file i have written something like this to make entry to table

Student.create(class_id:2 ,marks:"abcdef", rank: 2)

when i add these data to table by rake db:seed command ,i was expecting i would not be allowed to add this ,because for marks field of student, string is being inserted instead of integer.But rails added this record without any problem.

so how do i ensure this kind of entry doesnot happen and my table ensures type check.Me a newbie to rails and postgres

Ok, add a validation inside the Student model to check the same. Then you will get the error. — Arup Rakshit
– Arup Rakshit, Commented Feb 28, 2016 at 18:13
@arupRakshit okay this is at the model level,but cant i do something at the db level ,so postgres donot provide something for it at db level? — Rumour
– Rumour, Commented Feb 28, 2016 at 18:21

Arup Rakshit · Accepted Answer · 2016-02-28 19:07:18Z

1

So, a validation like below will work. Add it to the Student model.

validates :marks, numericality: { only_integer: true }

Whenever you will try to create a Student record, this validation will be called by Rails. If it passes then the recored will be created, otherwise not. There are methods to check if a record is valid or not in rails.

Read the guide to know how validation works in rails.

edited Feb 28, 2016 at 19:07

answered Feb 28, 2016 at 18:15

Arup Rakshit

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3 Comments

Arup Rakshit Over a year ago

@Rumour May be. But Doing it in ActiveRecord will have benefits when you are in Rails.

Rumour Over a year ago

i was expecting a error or exception , but the above statement simply doesnot add the row which contains a field who's value is wrong.

Arup Rakshit Over a year ago

@Rumour have you done a little study on Rails. Seems not. So please go through guides.rubyonrails.org/active_record_validations.html . Try Student.create!(class_id:2 ,marks:"abcdef", rank: 2) and see what goes on.

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