CODEWITHSUNDEEP
ruby
Becca
Becca

Reputation: 145

Why doesn't initialize appear as a method when I call on the instance methods of a class?

I'm writing a blog post on how almost everything is an object in Ruby, and I'm trying to show this through the following example:

class CoolBeans
  attr_accessor :beans

  def initialize
    @bean = []
  end

  def count_beans
    @beans.count
  end 

end

So from looking at the class we can tell it has 4 methods(unless of course, I'm wrong):

  1. It can initialize a default empty array of beans when a new instance is created
  2. It can count how many beans it has
  3. It can read how many beans it had (through the attr_accessor)
  4. It can write(or add) more beans to the empty array (also through the attr_accessor)

However, when I ask the class itself what instance methods it has, I don't see the default initialize method:

CoolBeans.new.class.instance_methods
# => [:beans, :beans=, :count_beans, :lm, :lim, :nil?, :===, :=~, :!~, :eql?, :hash, :<=>, :class, :singleton_class, :clone, :dup, :itself, :taint, :tainted?, :untaint, :untrust, :untrusted?, :trust, :freeze, :frozen?, :to_s, :inspect, :methods, :singleton_methods, :protected_methods, :private_methods, :public_methods, :instance_variables, :instance_variable_get, :instance_variable_set, :instance_variable_defined?, :remove_instance_variable, :instance_of?, :kind_of?, :is_a?, :tap, :send, :public_send, :respond_to?, :extend, :display, :method, :public_method, :singleton_method, :define_singleton_method, :object_id, :to_enum, :enum_for, :==, :equal?, :!, :!=, :instance_eval, :instance_exec, :__send__, :__id__]

Does this mean that the initialize method is not an instance method? If not, why isn't it showing up as a method available to the class CoolBeans?

Upvotes: 6

Views: 229

Answers (1)

Yu Hao
Yu Hao

Reputation: 122383

instance_methods returns an array of public and protected methods. However, initialize is automatically private ref.

CoolBeans.private_instance_methods
# => [:initialize, :default_src_encoding, :irb_binding, :initialize_copy, :initialize_dup, :initialize_clone, :sprintf, :format, :Integer, :Float, :String, :Array, :Hash, :warn, :raise, :fail, :global_variables, :__method__, :__callee__, :__dir__, :eval, :local_variables, :iterator?, :block_given?, :catch, :throw, :loop, :respond_to_missing?, :trace_var, :untrace_var, :at_exit, :syscall, :open, :printf, :print, :putc, :puts, :gets, :readline, :select, :readlines, :`, :p, :test, :srand, :rand, :trap, :load, :require, :require_relative, :autoload, :autoload?, :proc, :lambda, :binding, :caller, :caller_locations, :exec, :fork, :exit!, :system, :spawn, :sleep, :exit, :abort, :Rational, :Complex, :set_trace_func, :gem, :gem_original_require, :singleton_method_added, :singleton_method_removed, :singleton_method_undefined, :method_missing]
#     ^^^^^^^^^^^

Upvotes: 10

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