Welcome to Ruby!

A quick poll

  • I'm familiar with the precious gem
  • I've dabbled in ruby before
  • I've used ruby in smaller projects
  • I'm a ruby God

How familiar are you with Ruby?

Everything is an object!

1.times
"hello".split
[].size
{}.merge({})
true.klass
def hello(some_arg)
    return 5
end

def hi(some_arg)
    5
end

>>> hello "arg"
5

>>> hi "arg"
5


>>> hi hello "arg" # NONONONONONOO
>>> hi(hello("arg")) # YES

Implicit Returns

camelCase = 2 # NO NONONONO
snake_case = 5 # Yes

class CamelCase # YES
...

class snake_case # NONONONO
...

Naming

Variables

foo = 5
baz = []
bar = {}
a = true
b = "hello"

Strings

a = "hello"
b = "world"

c = "#{a} #{b}"

>>> puts c
"hello world"

Interpolation

a = "hello "
a << "world"

>>> puts a
"hello world"

Substrings

a = "hello world"

>>> a[1..2]
"el"

>>> a[1...2]
"e"

Booleans

Everything is true....

...except nil and false

>>> puts true if "hello"
true

>>> puts true if 0
true
>>> puts "nope" if nil

>>> puts "nope" unless false
"nope"

Arrays

a = [1,2,3]

>>> a.first
1

>>> a.last
3

>> a[0]
1
>>> Array.new(3, 0)
[0,0,0]

We'll come back to arrays in a bit!

Hashes

Python dictionaries

{
    :a => 1,
    :b => 2,
}
{
    a: 1,
    b: 2,
}
{
    "a" => 1,
    "b" => 2,
}

Symbols

Kind of like strings, but not really.

(they don't have string methods)

>>> :hello = 5
SyntaxError: syntax error, unexpected '=', expecting end-of-input

Can't be mutated

a = :"helloworld"

>>> puts a
helloworld

>> a
:helloworld


>>> :helloworld == "helloworld"
false

Classes & Methods

class MyClass < ParentClass
    
    def self.class_method
        puts "this is a class method"
    end

    def instance_method(arg="default")
        puts arg
    end

    private

    def snake_case
    end

    protected

    def baz
    end

end

>>> MyClass.class_method
"this is a class method"

>>> instance = MyClass.new
>>> instance.instance_method "hello"
"hello"

>>> instance = MyClass.new
>>> instance.instance_method
"default"

Control Blocks

if true
    1
elsif a == 5
    2
else
    3
end
list = ['a', 'b', 'c']
for element in list:
    print(element)
['a', 'b', 'c'].each { |element| puts element }
['a', 'b', 'c'].each do |element|
    puts element
end

Python

Ruby

Blocks

Similar to lambda expressions in Python

lambda x: x % 3 == 0
{ |element| puts element }
lambda x: print(x)

Equals

Control Blocks II

Other useful blocks

>>> [1,2,3].map { |n| n * 2 }
[2, 4, 6]

>>> 3.times { puts 5 }
5
5
5

>>> [1,2,3].select { |n| n % 2 == 0 }
[2]

>> [1,2,3].any? { |n| n % 2 == 0 }
true

>>> [1,2,3].max_by { |n| n }
3

See the Ruby Enumerable documentation for more!

Thanks for coming!

Fall 2015 - Lecture 1: Ruby

By Rails Decal

Fall 2015 - Lecture 1: Ruby

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