Crecto

Crecto

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Crecto::Model

Last updated 3 months ago
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Application data models should inherit from Crecto::Model

class User < Crecto::Model

The Crecto::Model class imposes the inherited which imports the correct schema modules and sets up class wide variables and constants used for keeping track of associations and field names.

Schema

Inside the data model is where the database schema is defined.

class User < Crecto::Model
    schema "users" do
        field :first_name, String
        field :last_name, String
    end
end

The shema macro takes one argument and an options tuple. The argument is the database table name. If your database table doesn't have a primary key, you can pass an option to disable it: schema "users", primary_key: false do

Default fields

By default Crecto assumes your table has the following column names defined id, created_at, and updated_at.

These can be easily overridden.

class User < Crecto::Model
    set_created_at_field :other_field_name
    set_updated_at_field nil # This table does not use an updated at field
    
    # This table does not have a primary key field
    schema "users", primary_key: false do
        # fields...
    end
end

Fields

Database table fields are defined using the field macro. The field macro takes 2 arguments, the column name as a Symbol and the column type, and an optional options tuple.

Field types

Int

field :first_field, Int32
field :second_field, Int64
field :third_field, Int16

Float

field :first_field, Float32
field :second_field, Float64

Bool

field :bool_field, Bool

String

field :string_field, String

Time

field :time_field, Time

Array, postgres only

field :first_field, Array(Int32)
field :second_field, Array(Float64)
field :third_field, Array(Bool)
field :fourth_field, Array(String)

Arrays can be queries using build-in postgres methods

Repo.all(User, Query.where("? = ANY(fourth_field)", "some_string"))

Json, postgres only

field :json_field, Json

Json fields can be both postgres json or jsonb types. If jsonb is used, those fields can be queried using build-in postgres methods.

Repo.all(User, Query.where("json_field @> '{\"test\": \"123\"}'")

Field options

class User < Crecto::Model    
    # primary_key : Specify a new primary key field
    field :uuid, String, primary_key: true
    
    # virtual : This field does not exist in the database and wont be pesisted.
    # but can be set and accessed on the model instance
    field :password_confirm, String, virtual: true
    
    # default : Specify a default value for the attribute
    field :is_admin, Bool, default: false
end

Enum fields

class Vehicle < Crecto::Model
    enum State
        OFF
        STARTING
        RUNNING
    end
    
    enum Make
        COUPE
        SEDAN
        HATCH
        TRUCK
    end
    
    schema "vehicles" do
        enum_field, :state, State
        enum_field, :make, Make, column_name: "vehicle_type", column_type: Int32
    end
end

Non-nillable attributes

If you with to access attributes of a model without having to check for nil, in the case that you are using a NOT NULL database constraint you can use the non-nillable attribute accessors.

CAUTION: Mis-use of this could lead to Nil reference runtime exceptions

user.age!
user.name!
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