auto_constructor

This README is the one indexed from the repository at its latest ref, not from the tag for this version.

# auto_constructor

Auto construct initialize methods for classes and structs

## Installation

Add this to your application's `shard.yml`:

```yaml
dependencies:
  auto_constructor:
    github: kostya/auto_constructor
```

## Usage

```crystal
require "auto_constructor"

struct A
  include AutoConstructor

  field :a, Int32
  field :b, String, default: "def"
  field :c, Int32
  field :d, String?
  field :e, Float64
end

p A.new(1, "what", 3, "bla", 1.0)                # => A(@a=1, @b="what", @c=3, @d="bla", @e=1.0)
p A.new(a: 1, b: "what", c: 3, d: "bla", e: 1.0) # => A(@a=1, @b="what", @c=3, @d="bla", @e=1.0)
p A.new(a: 1, c: 3, e: 1.0)                      # => A(@a=1, @b="def", @c=3, @d=nil, @e=1.0)
p A.new({:a => 1, :c => 3, :e => 1.0})           # => A(@a=1, @b="def", @c=3, @d=nil, @e=1.0)
p A.new({"a" => 1, "c" => 3, "e" => 1.0})        # => A(@a=1, @b="def", @c=3, @d=nil, @e=1.0)
```

## Fields options

```
  :default - set default value
  :getter - (enabled by default, false to disable)
  :setter - (enabled by default, false to disable)
```

## After initialize hook

```crystal
require "auto_constructor"

class A
  include AutoConstructor
  field :x, Int32

  property y : Int32

  after_initialize do
    @y = @x + 1
  end
end

p A.new(1) # => #<A:0x10befc0 @x=1, @y=2>
```

## Auto expanding classes

```crystal
require "auto_constructor"

# some base class
class A
  include AutoConstructor
  field :x, Int32
end

# some user code extend this class, with another field
class A
  field :y, String
end

p A.new(1, "bla") # => #<A:0x1032d2f00 @x=1, @y="bla">
```

## Example usage with auto_json and auto_msgpack

```crystal
require "auto_json"
require "auto_msgpack"

struct Person
  include AutoJson
  include AutoMsgpack

  field :name, String
  field :age, Int32
  field :email, String?, json_key: "mail"
  field :balance, Float64, default: 0.0, json: false
  field :data, String?, msgpack: false
end

person = Person.new(name: "Vasya", age: 20, balance: 10.0, email: "bla@ru")
p person # => Person(@age=20, @balance=10.0, @data=nil, @email="bla@ru", @name="Vasya")

json = person.to_json
puts json # => {"name":"Vasya","age":20,"mail":"bla@ru"}

person2 = Person.from_json(json)
p person2 # => Person(@age=20, @balance=0.0, @data=nil, @email="bla@ru", @name="Vasya")

msgpack = person2.to_msgpack
puts msgpack # => Bytes[132, 164, 110, ...]

person3 = Person.from_msgpack(msgpack)
p person3 # Person(@age=20, @balance=0.0, @data=nil, @email="bla@ru", @name="Vasya")
```