Practice

Ruby exercises

Make a change, predict what it will do, and compare the result.

1
Ruby Basics
Store text and print it.
Adapt the lesson example. Change one value or element, predict the result, and explain why it changes.
Review lesson →Open compiler
Show starting example
Ruby
```
name = "Ada"
puts "Hello, #{name}"
```
2
Ruby Arrays
Visit each value in an array.
Adapt the lesson example. Change one value or element, predict the result, and explain why it changes.
Review lesson →Open compiler
Show starting example
Ruby
```
scores = [82, 91, 76]
scores.each do |score|
  puts score
end
```
3
Ruby Methods and map
Define a method and transform an array with map.
Predict [1, 2, 3].map { |n| n + 10 }.
Reveal answer and reasoning
It returns [11, 12, 13].
Review lesson →Open compiler
Show starting example
Ruby
```
def average(values)
  values.sum / values.size.to_f
end

puts average([82, 91, 76, 95])
puts [1, 2, 3].map { |n| n * n }.inspect
```
4
Ruby Classes
Keep state in an instance variable and read it with attr_reader.
Make Counter writable too.
Reveal answer and reasoning
Replace attr_reader with attr_accessor :value so counter.value = 5 works.
Review lesson →Open compiler
Show starting example
Ruby
```
class Counter
  attr_reader :value

  def initialize
    @value = 0
  end

  def increment
    @value += 1
  end
end

counter = Counter.new
counter.increment
counter.increment
puts counter.value
```
5
Ruby Hashes
Store key-value pairs and iterate over them.
What does scores["Zed"] return?
Reveal answer and reasoning
nil, because that key is absent.
Review lesson →Open compiler
Show starting example
Ruby
```
scores = { "Ada" => 91, "Grace" => 88 }
scores["Linus"] = 79
scores.each do |name, score|
  puts "#{name}: #{score}"
end
puts scores.size
```

Ruby Basics

Ruby Arrays

Ruby Methods and map

Ruby Classes

Ruby Hashes