Tipos, Clases y Módulos

Los métodos introspectivos mas usados son los que determinan el tipo de un objeto.

>> obj = [1, {:a => 2}]
=> [1, {:a=>2}]
>> obj.class                      # retorna la clase de un objeto
=> Array
>> obj.class.superclass           # retorna la superclase de un objeto
=> Object
>> obj.instance_of? Object        # determina si obj.class == Object
=> false
>> obj.instance_of? Array
=> true
>> obj.is_a? Object               # determina si obj es de una subclase de Object
=> true
>> obj.is_a? Array
=> true
>> obj.kind_of? Object            # kind_of? es un sinónimo de is_a?
=> true
>> Array === obj                  # equivalente a obj.is_a? Array
=> true
>> Object === obj
=> true
>> obj.respond_to? 'each'        # si tiene un método público o protected llamado 'each'
=> true                          # si se le pasa true como segundo argumento se comprueban
                                 # también los privados
>> Array.instance_methods(false) 
=> ["insert"
 "sort" "include?" "size" "&" "to_ary" "clear" "yaml_initialize" "shuffle"
 "replace" "pack" "zip" "flatten!" "to_s" "pop" "pretty_print_cycle" "hash"
 "cycle" "*" "indices" "nitems" "index" "collect" "+" "compact!"
 "last" "rassoc" "count" "drop" "delete" "delete_at" "combination" "collect!"
 "select" "each_index" "-" "flatten" "eql?" "fill" "length" "uniq!"
 "at" "choice" "reject!" "[]" "take" "inspect" "shift" "compact"
 "pretty_print" "[]=" "|" "find_index" "slice!" "each" "empty?" "transpose"
 "<<" "frozen?" "rindex" "map" "reverse_each" "reverse!" "to_a" "push"
 "uniq" "delete_if" "first" "product" "drop_while" "concat" "reject"
 "map!" "join" "slice" "indexes" "taguri" "<=>" "assoc" "fetch" "to_yaml"
 "==" "values_at" "permutation" "take_while" "unshift" "reverse"
 "sort!" "shuffle!"  "taguri="]