Crystal micro-orm library, similar to what dapper supplies for .NET Core
Main features:
SQL result sets to be transformed into an object or array of object
SQL scripts to be injected with the correct variables from the passed object
For the mapping to work (rs -> object) the column name in the result set must match the class' attribute name
Uses the JSON library from stdlib to allow from_json to be used to prevent the need for messy custom initializers on each class.
Simply include Objectify::Mappable in classes that will be created from a SQL result set
This include is not needed if your class is using JSON.mapping
Add this to your application's shard.yml:
dependencies:
objectify:
github: drum445/objectifyrequire "objectify"
# include objectify's mappable in your class
class Foo
include Objectify::Mappable
endrequire "db"
require "mysql"
require "objectify"
# Your class that is to be built from SQL, will raise exception if:
# A non-nillable field is not in the result set
# Or a field in the result set does not match the attribute's type
class Note
include Objectify::Mappable
property note_id : String
property content : String
property likes : Int64
property updated : Time
def initialize(@note_id, @content, @likes, @updated)
end
end
db = DB.open "mysql://root:password@localhost:3306/test"
db.query "SELECT '123' as note_id, 'hello' as content, 4 as likes, NOW() as updated FROM DUAL;" do |rs|
note = Objectify.to_one(rs, Note)
puts note # => Note Object
endrequire "db"
require "mysql"
require "objectify"
# Your class that is to be built from SQL
class Note
include Objectify::Mappable
property note_id : String
property content : String
property likes : Int64
property updated : Time? # nillable as it is not in the result set
end
db = DB.open "mysql://root:password@localhost:3306/test"
db.query "SELECT '123' as note_id, 'hello' as content, 4 as likes FROM DUAL
UNION ALL
SELECT '444', 'asd', 66 FROM DUAL;" do |rs|
notes = Objectify.to_many(rs, Note)
puts notes # => Array of Note
end
I prefer using the explicit "to_one" or "to_many" methods however if you like you can use Object.from_rs(rs) instead This will work with arrays or single objects
db.query "SELECT '123' as id, 'drum445' as username FROM DUAL;" do |rs|
person = Person.from_rs(rs)
people = Array(Person).from_rs(rs)
puts person # => Person Object
puts people # => Array of Person
endAs we are using the JSON::Serializable module we can take advantage of this:
https://crystal-lang.org/api/0.25.1/JSON/Serializable.html
Allowing us to have different column names in the result set map to our class attributes
require "db"
require "mysql"
require "objectify"
class Person
include Objectify::Mappable
@[JSON::Field(key: "id", emit_null: true)]
property person_id : String
property username : String
property created : Time?
def initialize(@person_id : String, @username)
end
end
db = DB.open "mysql://root:password@localhost:3306/test"
# id will map to Person.person_id due to JSON::Field settings
db.query "SELECT '123' as id, 'drum445' as username FROM DUAL;" do |rs|
person = Objectify.to_one(rs, Person)
puts person # => Person Object
endrequire "db"
require "mysql"
require "objectify"
db = DB.open "mysql://root:password@localhost:3306/test"
class Person
property id : String
property username : String
def initialize(@id, @username)
end
end
# create a person object and insert it into the db
p = Person.new("1234", "test")
query, args = Objectify.to_sql("INSERT INTO person (person_id, username) VALUES({id}, {username})", p)
db.exec query, argsChecks for required fields (non nillable) Result set is missing required field: foo
Checks for correct data type: Invalid data type for field: foo
- drum445 ed - creator, maintainer