A.8 Array
list of objects represented with square brackets, [].
A.8.1 Creating an Array
Array.new ⇒ Array
initializes a new empty Array.
cities = Array.new # => cities = []
or
cities = [] # => cities = []
A.8.2 .push
Array#push(Object) ⇒ Array
Adds elements to the end of an Array. Returns the modified Array.
cities.push("Chicago")
cities.push("Los Angeles")
cities.push("New York City")or
cities = ["Chicago", "Los Angeles", "New York City"]
# Initializes and adds elements to an ArrayA.8.3 .at()
Array#.at(Integer) ⇒ Object
Takes an Integer argument and return the element in that position of an Array. The following lines of code show the various forms of the .at method and return the same output.
Returns an Object
cities = ["Chicago", "Los Angeles", "New York City"]
cities.at(2)
cities.[](2)
cities[2]
"New York City"
Note:
1. Ruby indexes the elements in an array starting at zero, that is, the first element of an array will have the index zero.
2. Trying to access an element using an index greater than the length of the array will give you nil.
cities.at(3) # => nil
3. Using a negative index will retrieve elements from the end of the least.
cities.at(-1) # => "New York City"
cities.at(-2) # => "Los Angeles"
cities.at(-3) # => "Chicago"
cities.at(-4) # => nil
A.8.4 .first and .last
Array#first ⇒ Object or Array#last ⇒ Object
Retrieves and returns the first or the last element of an array.
Returns an Object
cities.first # => "Chicago"
cities.last) # => "New York City"
A.8.5 .index
Array#index(Object) ⇒ Integer
Returns an Integer that is the index of an element.
cities.index("Los Angeles") # => 1
A.8.6 .count
Array#count ⇒ Integer or Array#count(Object) ⇒ Integer
Returns the number of elements in a list, when give no arguments. If given an argument, returns the number of times that arguments occurs in the array. In both instances, this method returns an Integer
nums = [8, 3, 1, 19, 23, 3]
nums.count # => 6
nums.count(3) # => 2
nums.count(2) # => 0A.8.7 .reverse (Array)
Array#reverse ⇒ Array
Returns a new ArrayArray with the elements of the original Array but in the reversed order.
nums.reverse # => [3, 23, 19, 1, 3, 8]
A.8.8 .sort
Array#.sort ⇒ Array
Returns a new Array with the elements of the original Array but in the sorted in increasing order.
nums.sort # => [1, 3, 3, 8, 19, 23]
A.8.9 .shuffle
Array#shuffle ⇒ Array
Returns a new Array with the elements of the original Array but with the order shuffled randomly.
nums.shuffle # => [3, 23, 8, 19, 1, 3]
nums.shuffle # => [19, 3, 1, 8, 3, 23]
A.8.10 .sample
Array#sample ⇒ Array
Returns a random element from the array.
nums.sample # => 23
nums.sample # => 3
A.8.11 .min and .max
Array#min ⇒ Object or Array#max ⇒ Object
Retrieve the elements of minimum and the maximum values in the array.
nums.min # => 1
nums.max # => 23
A.8.12 .sum (Array)
Array#sum
Returns the sum of all the elements in the array.
nums.sum # => 57
Note This method only works in the elements in the Array are not a Hash