Enough Ruby to get started with Rails

getting_started.rb

#### Basic data types you need to know ####

nil
"String"
:Symbol # immutable; often used as identifiers for methods or properties, esp. as keys of hashes
1.is_a? Integer # true
1.0.is_a? Float # true

# Arrays:
my_array = []
my_array2 = Array.new

# Hash:
my_hash = {}
my_hash2 = Hash.new
my_hash3 = { hello: 'world' } # also sometimes seen as { :hello => 'world' }
                              # or with string keys: { 'hello' => 'world }

# it is super easy to compare arrays and hashes, even if they are fully of complex objects (or nested)
my_array == my_array2 # true
my_hash == my_hash2 # true

# Reading from both arrays and hashes is done with '[]'; '.' is reserved for method calls
my_array << 'hi'
my_array[0] # 'hi'

my_hash[:hello] = 'world'
my_hash[:hello] # 'world'
my_hash.length # 1
my_hash.hello # undefined method 'hello' for Hash

my_hash4 = { { hash_as_key: true} => 10 } # anything can be the key of a hash - even another hash
my_hash4[{ hash_as_key: true }] # 10


#### classes ####

# super easy to define a class
class MyClass
end

# or a class with inheritance
class SpecialString < String
end

# methods are public by default, but can also be protected or private. Anything defined below a `protected` or `private`
# will still be protected/private
class MyString < String
  def public_by_default
    1
  end
  
  protected
  
  def protected_method1
    'hello'
  end
  
  def protected_method2
  end
  
  private
  
  def private_method1
    'I am private'
  end
  
  def private_method2
    'I am also private'
  end
end

#### Loops ####
# Ruby tends to use iterators rather than explicit `for` loops.
# It has a very rich standard library with more or less something for everything
my_arr = [1,2,3,4,5,6]
# log each item in an array
my_arr.each do |number|
  p number
end

sum_by_doubles = my_arr.sum do |number|
  number * 2
end

evens = my_arr.filter do |number|
  number % 2 == 0
end


### Other useful things to remember ###

# methods always have an implicit return
def number
  1
end

number # returns 1

# methods don't need parentheses to be called. This is helpful with chaining

def nested_arr
  [ ['hello'] ]
end

nested_arr.first.first.length > 0

# parentheses are optional for passing arguments

def m1(a, b, c, d)
end

m1 0, 1, 2, 3