Class: Hashery::PropertyHash

Inherits:
CRUDHash show all
Defined in:
lib/hashery/property_hash.rb

Overview

A PropertyHash is the same as a regular Hash except it strictly limits the allowed keys.

There are two ways to use it.

1) As an object in itself.

h = PropertyHash.new(:a=>1, :b=>2)
h[:a]        #=> 1
h[:a] = 3
h[:a]        #=> 3

But if we try to set key that was not fixed, then we will get an error.

h[:x] = 5    #=> ArgumentError

2) As a superclass.

class MyPropertyHash < PropertyHash
  property :a, :default => 1
  property :b, :default => 2
end

h = MyPropertyHash.new
h[:a]        #=> 1
h[:a] = 3
h[:a]        #=> 3

Again, if we try to set key that was not fixed, then we will get an error.

h[:x] = 5    #=> ArgumentError

Constant Summary

Constants inherited from CRUDHash

CRUDHash::NA

Class Method Summary collapse

Instance Method Summary collapse

Methods inherited from CRUDHash

#<<, #[], [], #[]=, auto, #cast, #cast_key, #default_proc, #delete, #each, #fetch, #key?, #key_proc, #key_proc=, #merge, #read, #replace, #retrieve, #to_hash, #update, #values_at

Methods inherited from Hash

create, #rekey, #rekey!, #retrieve, #to_hash, #to_stash

Constructor Details

#initialize(properties = {}, &default_proc) ⇒ PropertyHash

Initialize new instance of PropertyHash.

Parameters:

  • properties (Hash) (defaults to: {}) —

    Priming properties with default values, or if it doesn’t respond to #each_pair, a default object.

  • default_proc (Proc) —

    Procedure for default value of properties for properties without specific defaults.



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# File 'lib/hashery/property_hash.rb', line 76

def initialize(properties={}, &default_proc)
  if properties.respond_to?(:each_pair)
    super(&default_proc)
    fixed = self.class.properties.merge(properties)
    fixed.each_pair do |key, value|
      store!(key, value)
    end
  else
    super(*[properties].compact, &default_proc)
  end
end

Class Method Details

.properties ⇒ Hash

Get a list of properties with default values.

Returns:

  • (Hash) —

    Returns Hash of properties and their default values.



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# File 'lib/hashery/property_hash.rb', line 44

def self.properties
  @properties ||= (
    parent = ancestors[1]
    if parent.respond_to?(:properties)
      parent.properties
    else
      {}
    end
  )
end

.property(key, opts = {}) ⇒ Object

Define a property.

Parameters:

  • key —

    Name of property.

  • opts (defaults to: {}) —

    Property options.

Options Hash (opts):

  • :default (Object) —

    Default value of property.

Returns:

  • default value.



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# File 'lib/hashery/property_hash.rb', line 64

def self.property(key, opts={})
  properties[key] = opts[:default]
end

Instance Method Details

#assert_key!(key) ⇒ Object (private)

Asserta that a key is a defined property.

Raises:

  • ArgumentError if key is not a property.



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# File 'lib/hashery/property_hash.rb', line 153

def assert_key!(key)
  unless key?(key)
    raise ArgumentError, "property is not defined -- #{key.inspect}"
  end
end

#property(key, opts = {}) ⇒ Object

Create a new property, on-the-fly.

Parameters:

  • key —

    Name of property.

  • opts (defaults to: {}) —

    Property options.

Options Hash (opts):

  • :default (Object) —

    Default value of property.

Returns:

  • default value.



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# File 'lib/hashery/property_hash.rb', line 101

def property(key, opts={})
  if opts[:default]
    store!(key, opts[:default])
  else
    store!(key, retrieve(key))
  end
end

#store(key, value) ⇒ Object

Store key value pair, ensuring the key is a valid property first.

Parameters:

  • key —

    The ‘Object` to act as indexing key.

  • value —

    The ‘Object` to associate with key.

Returns:

  • value.

Raises:

  • ArgumentError if key is not a valid property.



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# File 'lib/hashery/property_hash.rb', line 119

def store(key, value)
  assert_key!(key)
  super(key, value)
end

#store! ⇒ Object (private)

Alias original #store method and make private.



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# File 'lib/hashery/property_hash.rb', line 89

alias :store! :store