DB::Serializable

The DB::Serialization module automatically generates methods for DB serialization when included.

Once included, ResultSet#read(t) populates properties of the class from the ResultSet.

Example

require "db"

class Employee
  include DB::Serializable

  property title : String
  property name : String
end

employees = Employee.from_rs(db.query("SELECT title, name FROM employees"))
employees[0].title # => "Manager"
employees[0].name  # => "John"

Usage

DB::Serializable was designed in analogue with JSON::Serializable, so usage is identical. However, like DB.mapping, DB::Serializable is strict by default, so extra columns will raise DB::MappingExceptions.

Similar to JSON::Field, there is an annotation DB::Field that can be used to set serialization behavior on individual instance variables.

class Employee
  include DB::Serializable

  property title : String

  @[DB::Field(key: "firstname")]
  property name : String?
end

DB::Field properties:

• ignore: if true, skip this field in serialization and deserialization (false by default)
• key: defines which column to read from a ResultSet (name of the instance variable by default)
• converter: defines an alternate type for parsing results. The given type must define #from_rs(DB::ResultSet) and return an instance of the included type.

DB::Serializable::NonStrict

Including this module is functionally identical to passing {strict: false} to DB.mapping: extra columns will not raise.

class Employee
  include DB::Serializable
  include DB::Serializable::NonStrict

  property title : String
  property name : String
end

# does not raise!
employees = Employee.from_rs(db.query("SELECT title, name, age FROM employees"))