Introducing Arrays

Warmup

Ruby Doc defines an array as “ordered, integer-indexed collections of any object.”

• What information can you pull out of that definition?
• Looking at the other information on that page, what can you tell about arrays?

Ordered

• Arrays store information in a particular order.
• Concepts like “first,” “last,” “fifth” apply to them.

Integer-Indexed

• Because they are ordered, we can access items in an array by their position in the array.
• We use the term index to refer to this position.
• Arrays use integers to identify these positions.
• Arrays do not store values at an index of 2.5, only at 2 or 3.

Collection of Any Object

• Arrays are a way to store groups of things.
• Ruby does not care what types of things we store in Arrays.

Overview: Fundamental Array Methods

• []
• count
• << / push
• unshift
• insert
• pop
• shift
• shuffle

In IRB

name_1 = "Josh"
name_2 = "Mike"
name_3 = "Lauren"

names = []

Count

names.count

« / Push

names << name_1
names.count
names
names.push(name_2)
name.count
names

Pick a way to add the third name to the names array. Add your own name to the array without storing it to a varible beforehand.

Unshift

name_4 = "Jeff"
names.unshift(name_4)
names.unshift("Sal")
names.count
names

[]

names[0]
names[3]
names[-1]
names.first
names.last

[]=

names[2] = "Ilana"
names
names[1] = "Sal"
names

Insert

names.insert(2, "Victoria")
names

Pop

names
popped_name = names.pop
popped_name
names

Shift

names
shifted_name = names.shift
shifted_name
names

Shuffle

shuffled = names.shuffle
names
shuffled

Each

first_initial = []
names.each do |name|
  first_initial << name[0]
end

names
first_initial

Summary

See lesson