someobject.methods.
Any array has lots of handy, built-in methods, which it gets from the Kernel module (mixed in by every object), the Enumerable module, and Array itself. (For example, somearray.shuffle returns a randomized version of the array.)
To see what comes from where, we'll make an array, and ask it: "array, please get me an alphabetized list of your methods, go through that list, and print a statement saying where each one was defined." (Thanks to several respondents on Stackoverflow for showing me this.)
The resulting list presents all kinds of opportunities for exploration. (For example, "tainted?" is very interesting.)
irb(main):001:0> a = Array.new
=> []
irb(main):002:0> a.methods.sort.collect {|m| puts "#{m} defined by #{a.method(m).owner}"}
& defined by Array
* defined by Array
+ defined by Array
- defined by Array
<< defined by Array
<=> defined by Array
== defined by Array
=== defined by Kernel
=~ defined by Kernel
[] defined by Array
[]= defined by Array
__id__ defined by Kernel
__send__ defined by Kernel
all? defined by Enumerable
any? defined by Enumerable
assoc defined by Array
at defined by Array
choice defined by Array
class defined by Kernel
clear defined by Array
clone defined by Kernel
collect defined by Array
collect! defined by Array
combination defined by Array
compact defined by Array
compact! defined by Array
concat defined by Array
count defined by Array
cycle defined by Array
delete defined by Array
delete_at defined by Array
delete_if defined by Array
detect defined by Enumerable
display defined by Kernel
drop defined by Array
drop_while defined by Array
dup defined by Kernel
each defined by Array
each_cons defined by Enumerable
each_index defined by Array
each_slice defined by Enumerable
each_with_index defined by Enumerable
empty? defined by Array
entries defined by Enumerable
enum_cons defined by Enumerable
enum_for defined by Kernel
enum_slice defined by Enumerable
enum_with_index defined by Enumerable
eql? defined by Array
equal? defined by Kernel
extend defined by Kernel
fetch defined by Array
fill defined by Array
find defined by Enumerable
find_all defined by Enumerable
find_index defined by Array
first defined by Array
flatten defined by Array
flatten! defined by Array
freeze defined by Kernel
frozen? defined by Array
grep defined by Enumerable
group_by defined by Enumerable
hash defined by Array
id defined by Kernel
include? defined by Array
index defined by Array
indexes defined by Array
indices defined by Array
inject defined by Enumerable
insert defined by Array
inspect defined by Array
instance_eval defined by Kernel
instance_exec defined by Kernel
instance_of? defined by Kernel
instance_variable_defined? defined by Kernel
instance_variable_get defined by Kernel
instance_variable_set defined by Kernel
instance_variables defined by Kernel
is_a? defined by Kernel
join defined by Array
kind_of? defined by Kernel
last defined by Array
length defined by Array
map defined by Array
map! defined by Array
max defined by Enumerable
max_by defined by Enumerable
member? defined by Enumerable
method defined by Kernel
methods defined by Kernel
min defined by Enumerable
min_by defined by Enumerable
minmax defined by Enumerable
minmax_by defined by Enumerable
nil? defined by Kernel
nitems defined by Array
none? defined by Enumerable
object_id defined by Kernel
one? defined by Enumerable
pack defined by Array
partition defined by Enumerable
permutation defined by Array
pop defined by Array
private_methods defined by Kernel
product defined by Array
protected_methods defined by Kernel
public_methods defined by Kernel
push defined by Array
rassoc defined by Array
reduce defined by Enumerable
reject defined by Array
reject! defined by Array
replace defined by Array
respond_to? defined by Kernel
reverse defined by Array
reverse! defined by Array
reverse_each defined by Array
rindex defined by Array
select defined by Array
send defined by Kernel
shift defined by Array
shuffle defined by Array
shuffle! defined by Array
singleton_methods defined by Kernel
size defined by Array
slice defined by Array
slice! defined by Array
sort defined by Array
sort! defined by Array
sort_by defined by Enumerable
taint defined by Kernel
tainted? defined by Kernel
take defined by Array
take_while defined by Array
tap defined by Kernel
to_a defined by Array
to_ary defined by Array
to_enum defined by Kernel
to_s defined by Array
transpose defined by Array
type defined by Kernel
uniq defined by Array
uniq! defined by Array
unshift defined by Array
untaint defined by Kernel
values_at defined by Array
zip defined by Array
| defined by Array
