Array is used to keep collection of objects. Array in ruby can have any type of objects together. Using array in ruby:

>> a = []
>> arr = [1, 0, 7]
>> arr[2] # => 7
>> arr.size # => 3

>> arr = ["string", 5, 0.8, true]

You can create an object of Array like this:

>> arr = Array.new([8,6,9]) #=> [8, 6, 9]

However ruby developer community prefer the symbolic way to define new array:
 

arr = []

Note: Array in ruby is dynamic in size, so need not to pass the size of array while create a new array object.

Pushing elements in array:

arr = []

arr.push(5) # => [5]
OR
arr << 5 #=> [5]

arr.push(3,4,1) # => [5,3,4,1]

Accessing value in array:

arr[0] # => 5
arr[-1] # => 1
arr.first # => 5
arr.last # => 1

Removing elements of array:

arr # => [5,3,4,1]

remove from top:
arr.pop # => 1

remove from bottom:
arr # => [5,3,4,1]

arr.shift # => 5
arr #=> [3,4,1]

Array of string:

%w{ this is an array}
#=> ["this", "is", "an", "array"]

Delete element in array:

arr = [8,9,6,9,3]

arr.delete(9)
#=> 9
arr
#=> [8,6,3]   removed all 9 from array

arr = [8,9,6,9,3]

arr.delete_at(3)  # delete at a given index
# => 9

arr
# => [8, 9, 6, 3]

Join in array:

arr = ["hello", "how", "are", "you"]
arr.join(" ")
# => "hello how are you"

Flatten in array (flat nested arrays):

 arr = [1,[2,3],[4,["a", nil]]]
 arr.flatten
 # => [1,2,3,4,"a",nil]

Compact in array (remove nil):

arr = [1, 5, "a", nil, 9, nil, 6]
arr.compact
# => [1, 5, "a", 9, 6]

inject with array:

[1,2,3].inject {|sum, n| sum + n } # take first element in sum
# => 6

inject can also take an initial value

[1, 2, 3].inject(5){|sum,x| sum + x }
# => 11

[1, 2, 3].inject(1){|product, x| product*x }
# => 6

[8, 9, 6, 9, 3].inject(0, :+) # in ruby 1.9 or above
# => 35

Iterators with array:

[1,2,3].each { |i| i + 1 } # each returns the array acted upon
=> [1,2,3]

[1,2,3].map { |i| i + 1 } # map returns new array
# => [2, 3, 4]

Shortcut methods with array:

[1, 2, 3].map(&:to_s)
 => ["1", "2", "3"]

["a", "b", "c"].map(&:upcase)
# => ["A", "B", "C"]

More methods:

["a","b","c"].include? "d" # if array include the element
# => false

["a","b","c"].include? "a"
# => true

["a","b","c"].size
# => 3

Range to array:

('a'..'i').to_a
 => ["a", "b", "c", "d", "e", "f", "g", "h", "i"]

(1..9).to_a
#=>[1, 2, 3,  arr = [1,[2,3],[4,["a", nil]]]
 arr.flatten
 # => [1,2,3,4,"a",nil]4, 5, 6, 7, 8, 9]