lua-di

Dependency injection library for Lua that supports constructor based injection.

Map constructor parameter names to Lua packages and constant values
Configure providers to dynamically build parameter types
Support for configuring types to be kept in singleton scope
Zero configuration/customisation of application required, exept for main module configuration itself

Install

Get this library using luarocks: http://luarocks.org/modules/djfdyuruiry/lua-di

Example

Given you have the following classes:

-- example/Printer.lua
local Printer = {}
Printer.__index = Printer

function Printer.new()
    return setmetatable({}, Printer)
end

function Printer.write(self, ...)
    print(...)
end

return Printer

-- example/App.lua
local App = {}
App.__index = App

function App.new(appConfig, printer, writer, message)
    return setmetatable(
    {
        appConfig = appConfig,
        printer = printer,
        writer = writer,
        message = message
    }, App)
end

function App.run(self)
    self.printer:write("Hello World")
    self.writer(self.message)

    print(self.appConfig.logPath)
end

return App

You can configure all your dependencies in one function, then build your application:

local DependencyInjectionModule = require "lua-di.DependencyInjectionModule"

-- build and configure your app module
local appModule = DependencyInjectionModule(function(config)
    -- bind constructor parameter names to Lua modules
    config.bindings.types.printer = "example.Printer"

    -- bind constructor parameter to constant value
    config.bindings.values.message = "Orders Recieved Captain"

    -- parameter values can be of any type
    config.bindings.values.writer = function(...)
        print(...)
    end
  
    -- bind constructor parameter name to custom type (not a Lua module)
    config.bindings.types.appConfig = "AppConfig"
  
    -- define a provider for your custom type (either a builder function or a constant)
    -- (you can also provide instances for a Lua Package name in config.providers if you wish)
    config.providers.AppConfig = function()
        return
        {
            logPath = "/var/log/app.log",
            counter = 5
        }
    end
    
    -- make injected AppConfig instance a singleton
    config.singletons.AppConfig = true
end)

-- build an instance of the entry point class, injecting your dependencies
local app = appModule.getInstance("example.App")

app:run()

You can also enable the auto configure option to parse Lua modules using parameter names, following the pattern module__full__path__type for your constructor parameters; note this is case sensitive.

Given this class:

-- example/AutoApp.lua
local AutoApp = {}
AutoApp.__index = AutoApp

function AutoApp.new(example__Printer)
    return setmetatable(
    {
        -- given there exists a class in 'example/Printer.lua'
        printer = example__Printer
    }, AutoApp)
end

function AutoApp.run(self)
    self.printer:write("Auto Hello World")
end

return AutoApp

You can enable autoconfiguration like so:

local DependencyInjectionModule = require "lua-di.DependencyInjectionModule"

local autoAppModule = DependencyInjectionModule(function(config)
    config.enableAutoConfiguration()
end)

local autoApp = autoAppModule.getInstance("example.AutoApp")

autoApp:run()

Note this library supports both standard Lua classes and functional style classes:

Lua Classes

-- SomeClass.lua
local SomeClass = {}
SomeClass.__index = SomeClass

function SomeClass.new(val)
    return setmetatable({}, SomeClass)
end

function SomeClass.method(self)
    -- do stuff
end

return SomeClass

declaration: local instance = SomeClass.new(val)

Functional Style

local SomeClass = function(val)
    local iAmPrivate = "secretStuff"

    local method = function()
        -- do stuff
    end

    return 
    {
        method = method
    }
end

return SomeClass

declaration: local instance = SomeClass(val)

See the example app in example.lua to get a full view of how to configure an application to use this Dependency injection library.

Shelim/lua-di

lua-di

Install

Example