active record in rails 5

Active Record in Rails 5

http://jyaasa.comCopyright 2017. Jyaasa Technologies.

Hello ! I am Neha Suwal


Associate Software Engineer Jyaasa Technologies


Instance Public methods:

attribute(name, cast_type, **options)

Defines an attribute with a type on this model. It will override the type of existing attributes if needed. This allows control over how values are converted when assigned to a model.

attribute :price_in_cents, :integer


name: The name of the methods to define attribute methods for, and the column which this will persist to.

cast_type: A symbol such as :string or :integer, or a type object to be used for this attribute.

options:

default - The default value to use when no value is provided. If this option is not passed, the previous default value (if any) will be used. Otherwise, the default will be nil.

array (PostgreSQL only)- specifies that the type should be an array (see the examples below).

range (PostgreSQL only)- specifies that the type should be a range (see the examples below).


The type detected by Active Record can be overridden

#generate a model named StoreDetail with a column price_in_cents whose data type is decimal

class StoreDetail < ApplicationRecordend

create_table :store_details do |t| t.decimal :price_in_cents

t.timestampsend

store_detail = StoreDetail.create(price_in_cents: '10.1')store_detail.price_in_cents #=>

#<BigDecimal:585ab10,'0.101E2',18(18)>


#in rails 5class StoreDetail < ApplicationRecord

attribute :price_in_cents, :integerend

store_detail.price_in_cents #=> 10


A default can also be provided

create_table :store_details do |t| t.decimal :price_in_cents

t.string :name, default: "original default" t.timestampsend

store_detail = StoreDetail.create(price_in_cents: '10.1')store_detail.name #=> “original default”


#in rails 5class StoreDetail < ApplicationRecord

attribute :name, :string, default: "new default"end

new_store_detail = StoreDetail.create(price_in_cents: '1000')new_store_detail.name #=> "new default"


Attributes do not need to be backed by a database column

class StoreDetail < ApplicationRecordattribute :price_in_cents, :integerattribute :name, :string, default: "new default"attribute :time, :datetime, default: -> { Time.now }

end

StoreDetail.new.time #=> Mon, 02 Jan 2017 04:48:24 UTC +00:00


class StoreDetail < ApplicationRecordattribute :price_in_cents, :integerattribute :name, :string, default: "new default"attribute :time, :datetime, default: -> { Time.now }attribute :field, :integer, array: true

end

store_detail = StoreDetail.new(field: ["1", "2", "3"])store_detail.field #=> [1, 2, 3]


store_detail.attributes #=> {"id"=>nil, "price_in_cents"=>nil, "name"=>"new default", "created_at"=>nil, "updated_at"=>nil, "time"=>Mon, 02 Jan 2017 04:52:25 UTC +00:00, "field"=>[1, 2, 3]}


Summary:

● The type detected by Active Record can be overridden.● A default can also be provided.● Attributes do not need to be backed by a database column.

References

http://edgeguides.rubyonrails.org/5_0_release_notes.htmlhttp://api.rubyonrails.org/classes/ActiveRecord/Attributes/ClassMethods.html


http://edgeguides.rubyonrails.org/5_0_release_notes.html#active-record

http://api.rubyonrails.org/classes/ActiveRecord/Attributes/ClassMethods.html

http://api.rubyonrails.org/classes/ActiveRecord/Attributes/ClassMethods.html

Thank You!Any Queries? Lets Discuss


active record in rails 5

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