Class: HashInitializedStruct

Inherits:
Object
  • Object
show all
Defined in:
lib/hash_initialized_struct.rb,
lib/hash_initialized_struct/version.rb

Overview

class Point < HashInitializedStruct(:x, :y); end Or: Point = HashInitializedStruct(:x, :y)

point = Point.new(x: 1, y: 2) point.x # => 1

point2 = Point.new(x: 1, y: 2, nonsense: “foobar”) # => raises ArgumentError

Constant Summary collapse

VERSION = 
"1.3.0"

Class Method Summary collapse

Class Method Details

.new(*attrs) ⇒ Object 



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# File 'lib/hash_initialized_struct.rb', line 16

def self.new(*attrs)
  symbol_attrs = attrs.map do |a|
    case a
    when Symbol
      a
    else
      a.to_sym.tap do |sym|
        raise TypeError, "Could not coerce #{a.inspect} to symbol" unless sym.kind_of?(Symbol)
      end
    end
  end

  Class.new self do
    const_set :STRUCT_ATTRS, symbol_attrs
    attr_accessor *symbol_attrs

    def self.new(*args, &block)
      self.subclass_new(*args, &block)
    end

    def initialize(attrs)
      attrs    = Hash(attrs)
      provided = attrs.keys
      needed   = needed_keys
      self.raise_on_unrecognised_keys(provided, needed)
      self.raise_on_missing_keys(provided, needed)
      set_attributes(attrs)
    end

    def to_h
      # [k,k,...] => [[k,v], [k,v], ...] => {k => v, k => v, ...}
      Hash[ self.class::STRUCT_ATTRS.map {|key| [key, self.public_send(key)]} ]
    end
    alias :to_hash :to_h

    protected

      def needed_keys
        self.class::STRUCT_ATTRS
      end

      def raise_on_unrecognised_keys(provided, needed)
        (provided - needed).tap do |unknown|
          raise ArgumentError, "Unrecognised keys: #{unknown.map(&:inspect).join(', ')}" unless unknown.empty?
        end
      end

      def raise_on_missing_keys(provided, needed)
        (needed - provided).tap do |missing|
          raise ArgumentError, "Missing keys: #{missing.map(&:inspect).join(', ')}" unless missing.empty?
        end
      end

      def set_attributes(attrs)
        attrs.each do |attr,value|
          instance_variable_set("@#{attr}", value)
        end
      end
  end
end

.subclass_new ⇒ Object 



13
 
# File 'lib/hash_initialized_struct.rb', line 13

alias :subclass_new :new