Object-relational mapping for Nim

This is ORM module for Nim language and its db_sqlite, db_mysql and db_postgres standard database modules.

Importing orm requires one of sqlite, mysql or postgres defines, since ORM module imports on of the databases.

Features

1. Turning Nim expressions into SQL syntax at compile time
2. Iterating through model objects based on given where(...)
3. NYI Storing model object changes via save()

Usage

1. Importing module and selecting database interface

   import orm_sqlite #<- for interfacing with sqlite
   # create empty in memory database
   Model.open("", "", "", "")
   Model.exec("CREATE TABLE User(name varchar(32), password varchar(32))", [])
   Model.exec("INSERT INTO User VALUES('joe', '123')", [])
   Model.exec("INSERT INTO User VALUES('ann', 'abc')", [])

2. Iterating through model objects based on given expression

   var password = "abc"
   var name = "ann"
   
   # expected: joe, ann
   for user in User.where((@password == "123" or @password == password) and
                         (@name == "joe" or @name == name)):
    echo user.name

Discussion

Nim has powerful AST rewriting capabilities via compile-time macros, this leads us to amazing optimizations while keeping application code nice, clean & at higher level.

Currently the module translates expressions into SQL calls at compile time, eg.:

var password = "abc"
var name = "ann"

for user in User.where((@password == "123" or @password == password) and
                       (@name == "joe" or @name == name)):

is translated to:

for user in User.fetch("SELECT `name`, `password` FROM `User` where
                        (`User`.`password` = '123' OR `User`.`password` = ?) AND
                        (`User`.`name` = 'joe' OR `User`.`name` = ?)",
                       password, name):

Comparing to other solutions such as ActiveModel from Ruby where such translation is done at runtime level, we got great performance boost and syntax error diagnostics already there at compile-time.

License

This module is released under MIT license:

Copyright (C) 2015 Adam Strzelecki

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.