maiha/crystal-orm.md

## crystal-orm.md

      
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              crystal-orm.md
            
          
    active_record.cr - Active Record pattern implementation


⚠️ activity last commit is 1 year ago
MySQL driver : libmysql(C API)
✅ agnostic FREE
✅ define fields simple
✅ table name supports camel class name
⬜ model level query lacks first, count
❌ low level adapter hard to access
⬜ relations
⚠️ multibytes can't set charset in default (needs monkey patch)
⬜ pluck not supported yet
⬜ gateway pattern not supported yet
⬜ timestamps not supported yet
✅ field access #foo returns Union(T, T::Null) with null object pattern
✅ required field access #foo
⬜ nilable field access not supported yet
⚠️ inspect class doesn't show column names
⚠️ inspect record ugly
✅ prepared statements uses : with hash, and returns Array(Array())

field access


Model#foo returns Union(T, T::Null) where T::Null is a null pattern object

usage

class User < ActiveRecord::Model
  adapter mysql
  primary id : Int
  field name : String
  field age  : Int
end

u = User.get(1)

u.name        # => "maiha"
u.name.class  # => String
u.name.upcase # => "MAIHA"
u.age         # => Null(struct)
u.age.class   # => Int::Null
u.age + 1     # => 1
u.age || -1   # => Null(struct)

p u
# #<User:0xaeeb60
#  @fields=
#   #<ActiveRecord::Model::Fields:0xaeeb40
#    @typed_fields=
#     {"Int" =>
#       #<ActiveRecord::Model::Fields::Generic(Int16 | Int32 | Int64 | Int8 | Int::Null | UInt16 | UInt32 | UInt64 | UInt8):0xaeeb20
#        @fields={"id" => 1_i64}>,
# ...
core - Pure, transparent and efficient ORM

crecto - Database wrapper, based on Ecto

granite-orm - ORM for Postgres, Mysql, Sqlite


✅ activity HIGH
MySQL driver : crystal-mysql
❌ agnostic controlled by Amber project
✅ define fields simple
⚠️ table name doesn't care camel class name (UserGroup → usergroups)
❌ adapter doesn't connect lazily (ENV["DATABASE_URL"] must be resolved in not runtime but class definitions)
✅ model level query CRUD and count
✅ relations
✅ multibytes
⬜ pluck not supported yet
⬜ gateway pattern not supported yet
⚠️ timestamps just a syntax sugar (names and types are fixed)
⚠️ field access #foo returns T?
✅ required field access #foo!
✅ nilable field access #foo
⚠️ inspect class doesn't show column names
✅ inspect record pretty (but multiline)
✅ prepared statements uses ? with array, and returns Array(MySql::ResultSet)

❌ It's hard to operate MySql::ResultSet for arbitrary fields


usage

class User < Granite::ORM::Base
  adapter mysql
  field name : String
  field age  : Int32
end

u = User.create(name: "maiha")
# => "INSERT INTO `users` (`name`, `age`) VALUES (?, ?): ["maiha", nil]"
u.name.upcase # undefined method 'upcase' for Nil (compile-time type is (String | Nil))
u.name!.upcase # => "MAIHA"
u.name!.upcase # => "MAIHA"
u.age       # => nil
u.age || -1 # => -1
u.age!      # raises "User#age cannot be nil" (Exception)
jennifer.cr - Active Record pattern implementation

record - Type safe querying, saving and updating

topaz - A simple and useful db wrapper