Class: Chef::Node::ImmutableMash

Inherits:
Mash show all
Includes:
Immutablize
Defined in:
lib/chef/node/immutable_collections.rb

Overview

ImmutableMash

ImmutableMash implements Hash/Dict behavior for reading values from node attributes.

ImmutableMash acts like a Mash (Hash that is indifferent to String or Symbol keys), with some important exceptions:

  • Methods that mutate state are overridden to raise an error instead.

  • Methods that read from the collection are overriden so that they check if the Chef::Node::Attribute has been modified since an instance of this class was generated. An error is raised if the object detects that it is stale.

  • Values can be accessed in attr_reader-like fashion via method_missing.

Constant Summary collapse

DISALLOWED_MUTATOR_METHODS = 
[
  :[]=,
  :clear,
  :collect!,
  :default=,
  :default_proc=,
  :delete,
  :delete_if,
  :keep_if,
  :map!,
  :merge!,
  :update,
  :reject!,
  :replace,
  :select!,
  :shift
]

Instance Method Summary collapse

Methods included from Immutablize

#immutablize

Methods inherited from Mash

#[]=, #default, #delete, #except, #fetch, from_hash, #initialize_copy, #key?, #merge, #regular_update, #regular_writer, #stringify_keys!, #symbolize_keys, #update, #values_at

Constructor Details

#initialize(mash_data) ⇒ ImmutableMash

Returns a new instance of ImmutableMash.



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# File 'lib/chef/node/immutable_collections.rb', line 152

def initialize(mash_data)
  mash_data.each do |key, value|
    internal_set(key, immutablize(value))
  end
end

Dynamic Method Handling

This class handles dynamic methods through the method_missing method

#method_missing(symbol, *args) ⇒ Object 



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# File 'lib/chef/node/immutable_collections.rb', line 175

def method_missing(symbol, *args)
  if args.empty?
    if key?(symbol)
      self[symbol]
    else
      raise NoMethodError, "Undefined method or attribute `#{symbol}' on `node'"
    end
  # This will raise a ImmutableAttributeModification error:
  elsif symbol.to_s =~ /=$/
    key_to_set = symbol.to_s[/^(.+)=$/, 1]
    self[key_to_set] = (args.length == 1 ? args[0] : args)
  else
    raise NoMethodError, "Undefined node attribute or method `#{symbol}' on `node'"
  end
end

Instance Method Details

#convert_value(value) ⇒ Object

Mash uses #convert_value to mashify values on input. Since we’re handling this ourselves, override it to be a no-op



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# File 'lib/chef/node/immutable_collections.rb', line 193

def convert_value(value)
  value
end

#dup ⇒ Object

NOTE: #default and #default= are likely to be pretty confusing. For a regular ruby Hash, they control what value is returned for, e.g.,

hash[:no_such_key] #=> hash.default

Of course, ‘default’ has a specific meaning in Chef-land



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# File 'lib/chef/node/immutable_collections.rb', line 202

def dup
  Mash.new(self)
end

#public_method_that_only_deep_merge_should_use(key, value) ⇒ Object 



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# File 'lib/chef/node/immutable_collections.rb', line 158

def public_method_that_only_deep_merge_should_use(key, value)
  internal_set(key, immutablize(value))
end

#to_hash ⇒ Object 



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# File 'lib/chef/node/immutable_collections.rb', line 206

def to_hash
  h = Hash.new
  each_pair do |k, v|
    h[k] =
      case v
      when ImmutableMash
        v.to_hash
      when ImmutableArray
        v.to_a
      else
        v
      end
  end
  h
end