# MooseX

A postmodern object DSL for Ruby [![Build Status](https://travis-ci.org/peczenyj/MooseX.png)](https://travis-ci.org/peczenyj/MooseX)

THIS MODULE IS EXPERIMENTAL YET! BE CAREFUL!

Talk is cheap. Show me the code!

```ruby
require 'moosex'

class Point
  include MooseX

  has x: {
    is: :rw,      # read-write (mandatory)
    isa: Integer, # should be Integer
    default: 0,   # default value is 0 (constant)
  }

  has y: {
    is: :rw,
    isa: Integer,
    default: lambda { 0 }, # you should specify a lambda
  }

  def clear! 
    self.x= 0      # to run with type-check you must
    self.y= 0      # use the setter instad @x=
  end

  def to_s
    "Point[x=#{self.x}, y=#{self.y}]"
  end 
end 

# now you have a generic constructor
p1  = Point.new                       # x and y will be 0
p2  = Point.new( x:  5 )              # y will be 0
p3  = Point.new( x:  5, y: 4)
```
    
## Installation

Add this line to your application's Gemfile:

    gem 'moosex'

And then execute:

    $ bundle

Or install it yourself as:

    $ gem install moosex

You need ruby 2.0.x or superior.

## Description

MooseX is an extension of Ruby object system. The main goal of MooseX is to make Ruby Object Oriented programming easier, more consistent, and less tedious. With MooseX you can think more about what you want to do and less about the mechanics of OOP. It is a port of Moose/Moo from Perl to Ruby world.

Read more about Moose on http://moose.iinteractive.com/en/

## Motivation

It is fun

## Usage

You just need include the MooseX module in your class and start to describe the attributes with our DSL. This module will inject one smart constructor, acessor and other necessary methods.

Instead the normal way of add accessors, constructor, validation, etc

```ruby
class Foo
  attr_accessor :bar, :baz, :bam

  def initialize(bar=0, baz=0, bam=0)
    unless [bar, baz, bam].all? {|x| x.is_a? Integer }
      raise "you should use only Integers to build Foo"
    end
    @bar = bar
    @baz = baz
    @bam = bam
  end
end
```
you can do this:

```ruby
class Foo
  include MooseX

  has [:bar, :baz, :bam], {
    is: :rw,
    isa: Integer,
    default: 0
  }
end
``` 

## DSL: the 'has' method

The key of the DSL is the 'has' method injected in your class. You should use this method do describe your class and define the behavior like this:

```ruby
has :attribute_name, { hash of properties }
```

to describe one new attribute you shoud specify some properties inside a Hash. The only mandatory property is the ':is', to specify how we should create the acessors (if public or private).

The options for "has" are as follows:

### is

**Required**, may be :ro, :rw, :rwp, :private or :lazy.

"ro" specify a read-only attribute - generate only the reader method - you should specify the value in the constructor or using "default".

"rw" specify a read-write attribute - generate both reader and writter methods.

"rwp" specify a read-write private attribute. Similar to "rw" but the writter is a private method.

"private" will generate both reader and writter as private methods

"lazy" similar to "ro", but also sets "lazy" to true and "builder" to "build_#{attribute_name}".

### isa

You can specify an optional type check for the attribute. Accepts a lambda, and it must raise one exception if the type check fails. If you provides a Class or Module, we will call the 'is_a?' method in the new value againt the Class/Module. We call the type check routine on the constructor and in each call of the writter method.

You can specify your own kind of type validation.
```ruby
    isa: lambda do |new_value|
      unless new_value.respond_to? :to_sym
        raise "bar should respond to to_sym method!"
      end
    end,
end
``` 

Important: if you access the attribute instance name using @attribute_name= you loose the type check feature. You need always set/get the attribute value using the acessors generated by MooseX.

### default

You can specify an optional default value to one attribute. If we don't specify in the constructor, we will initialize the attribute with this value. You also can specify one lambda to force object creation.

```ruby
  default: 0,
```
or
```ruby
  default: lambda{ MyObject.new },
```

### coerce

You can try to coerce the attribute value by a lambda before the type check phase. For example you can do

```ruby
  coerce: lambda{ |new_value| new_value.to_i },
```

to force a convertion to integer. Or flatten one array, convert to symbol, etc. Optional.

### handles

One of the greatest features in MooseX: you can inject methods and delegate the method calling to the attribute. For example, instead do this:

```ruby
  def some_method(a,b,c)
    @attribute.some_method(a,b,c)
  end
```

you simply specify one or more methods to inject.
```ruby
  handles: [:some_method],
```
If you specify one Module or Class, we will handle all public instance methods defined in that Module or Class ( if Class, we will consider all methods except the methods declared in the superclass). The only limitation is BasicObject (forbidden).

If you need rename the method, you can specify a Hash:
```ruby
  handles: {
    my_method_1: :method1,
    my_method_2: :method2,
  },
```

Optional.

### trigger

You can specify one lambda or method name to be executed in each writter ( if coerce and type check does not raise any exception ). The trigger will be called in each setter and in the constructor if we do not use the default value. Useful to add a logging operation or some complex validation.

```ruby
  trigger: lambda {|object, new_value| object.logger.log "change the attribute value to #{new_value}" }
```
or
```ruby
has a: { is: :rw }
has b: {
  is: :rw,
  trigger: :verify_if_a_and_b_are_different,
  }
...
  def verify_if_a_and_b_are_different(new_value_of_b)
    if self.a.eql? new_value_of_b
      raise "a and b should be different!"
    end
  end
```

Optional.

### writter

You can specify the name of the attribute acessor, default is "#{attribute_name}=".

### reader

You can specify the name of the attribute acessor, default is "attribute_name".

### predicate

Creates a method who returns a boolean value if the attribute is defined. If true, will create one public "has_#{attribute_name}?" method by default.

For example 
```ruby
class Foo
  include MooseX

  has x: {
    is: :rw,
    predicate: true,
  }
end

foo = Foo.new
foo.has_x?     # returns false
foo.x= 10
foo.has_x?     # returns true
```
Important: nil is different than undefined. If you do not initialize one attribute, you will receive one 'nil' if you try to fetch the value, but the state of this attribute is 'undefined'. If you set any value (even nil), the attribute will be considered 'defined' and the predicate will return true.

Optional.

### clearer

Creates a method who will unset the attribute. If true, will create one public "clear_#{attribute_name}!" method by default. Unset in this case is not 'nil', we will remove the instance variable. For example:

```ruby
class Foo
  include MooseX

  has x: {
    is: :rw,
    predicate: true,
    clearer: true,
  }
end

foo = Foo.new
foo.has_x?     # returns false
foo.x= 10
foo.has_x?     # returns true
foo.clear_x!   # will unset the attribute x
foo.has_x?     # returns false
```
Optional.

### init_arg

You can rename the attribute name in the constructor. For example:

```ruby
class Foo
  include MooseX

  has secret: {
    is: :rw,
    writter: :x=,
    reader: :x,
    init_art: :x,
  }
end

foo = Foo.new(x: 1)  # specify the value of secret in the constructor
foo.x                # return 1 
foo.x= 2             # will set 'secret' to 2
```

### lazy

Another great feature: lazy attributes. If you this to true, we will wait until the first reader accessor be called to create the object using the builder method, then store the value. For example:

```ruby
class Foo
  include MooseX

  has x: {
    is: :rw,
    lazy: :true,
    predicate: true,  # predicate and clearer are just
    clearer: true,    # to show a better example
  }

  def builder_x
    Some::Class.new
  end
end

foo = Foo.new  # normal...
foo.has_x?     # returns false
foo.x          # will call the builder_x method and store the value
foo.has_x?     # returns true
foo.x          # returns the stored value
foo.clear_x!   # will unset the attribute x
foo.has_x?     # returns false
foo.x          # will call the builder again and store the value
```
A lazy attribute needs a builder method or lambda. By default you should implement the "builder_#{attribute_name}" method. Using lazy you should initialize one attribute when you really need.

Optional.

### builder

You can specify the builder name if the attribute is lazy, or you can specity one lambda. If true, the default name of the builder will be "builder_#{attribute_name}". This attribute will be ignored if the attribute is not lazy.

```ruby
class Foo
  include MooseX

  has x: {
    is: :rw,
    lazy: :true,
    builder: lambda{ |foo| Some::Class.new } # you can ignore foo, or use it!
  }
end
```
Optional.

## BUILD

If you need run some code after the creation of the object (like some extra validation), you should override the BUILD method.

```ruby
class BuildExample 
  include MooseX

  has [:x, :y], {
    is: :rw,
    required: true,
  }
  def BUILD
    if self.x == self.y 
      raise "invalid: you should use x != y"
    end 
  end
end

b1 = BuildExample.new(x: 1, y: 2) # will create the object 
b2 = BuildExample.new(x: 1, y: 1) # will raise the exception!
```ruby

### BUILDARGS

If you need manupulate the constructor argument list, you should implement the method BUILDARGS. You MUST return one Hash of attribute_name => value.

```ruby
class BuildArgsExample2 
  include MooseX

  has [:x, :y], {
    is: :rw,
    required: true,
  }

  def BUILDARGS(x=4,y=8)
    args = {}
    args[:x] = x
    args[:y] = y
    
    args
  end
end

ex1 = BuildArgsExample2.new(1,2) # x == 1, y == 2
ex2 = BuildArgsExample2.new(1)   # x == 1, y == 8
ex3 = BuildArgsExample2.new()    # x == 4, y == 8
```

## IMPORTANT

This module is experimental. I should test more and more to be possible consider this "production ready". If you find some issue/bug please add here: https://github.com/peczenyj/MooseX/issues

Until the first 0.1 version I can change anything without warning.

I am open to suggestions too.

## TODO

1. Support to Roles ( it is a Module on Steroids )
2. Support to after/before/around 
3. Improve the typecheck system (we should specify: we need an array of positive integers)
4. Improve the exception and warning system
5. Profit!

## Limitations

Experimental module, be careful.

Now has limited support to subclassing.

## Contributing

1. Fork it ( http://github.com/peczenyj/MooseX/fork )
2. Create your feature branch (`git checkout -b my-new-feature`)
3. Commit your changes (`git commit -am 'Add some feature'`)
4. Push to the branch (`git push origin my-new-feature`)
5. Create new Pull Request