hashes.rb

# frozen_string_literal: true

# Hashes
# In order to build a hash you must use curly braces - Hashes must have value pairs

hash = {
  'title' => 'Jurassic Park',
  'director' => 'Steven Spielberg',
  'film_id' => '768646',
  'original_language' => 'english'
}

# This array will contain the information about Jurassic Park

# To access the values stored in the hash you access their value

puts hash['director']
# outputs "Steven Spielberg"

----------------------------------------
h1 == h2
# Return true if h1 and h2 contain the same number of keys and if each key-value pair is equal
h[key]
# Element Reference - retrieve the value object corresponding to the key object of hash h
h[key] = value
# Set the value of key of hash h
h.clear
# Remove all key-value pairs from hash h
h.empty?
# Return true if hash h contains no key-value pairs
h.length
# Return the number of key-value pairs in hash h (option 1)

# Enumerating I
h.delete_if
# Delete every key-value pair from hash h for which block evaluates to true
h.each
# Call block once for each key in hash h, passing the key-value pair as parameters (option 1)
h.each_key
# Call block once for each key in hash h, passing the key as a parameter
h.each_value
# Call block once for each key in hash h, passing the value as a parameter
h.keep_if
# Delete every key-value pair from h for which block evaluates to false

# Enumerating II
h.any?
# Pass each key, value of hash h to a block and return true if given block ever returns a value other than false or nil.
h.each_pair
# Call block once for each key in hash h, passing the key-value pair as parameters (option 2)
h.reject
# Return a new hash consisting of entries for which the block returns false of hash h
h.reject!
# Equivalent to delete_if, but return nil if no changes were made to hash h
h.select
# Return a new hash consistent of entries for which the block returns true for hash h
h.select!
# Equivalent to keep_if, but return true if no changes were made to hash h

# Keys I
h.delete(key)
# Delete key-value pair and return value from hash h whose key is equal to key
h.key?(key)
# Return true if the given key is present in hash h (option 1)
h.include?(key)
# Return true if the given key is present in hash h (option 2)
h.key(value)
# Return the key of an occurrence of a given value in hash h
h.key?(key)
# Return true if the given key is present in hash h (option 3)
h.keys
# Return a new array populated with the keys from hash h
h.member?(key)
# Return true if the given key is present in hash h (option 4)

# Values I
h.default
# Return default value of hash h
h.default = obj
# Set default value of hash h to obj
h.default_proc
# If hash h was invoked with a block, return that block
h.default_proc = block
# Set default proc of hash h to be executed on each failed key lookup of h
h.fetch(key)
# Return a value from hash h for key. Raise exception if key not found.
h.value?(value)
# Return true if the given value is present for some key in hash h (option 1)
h.value?(value)
# Return true if the given value is present for some key in hash h (option 2)
h.values
# Return a new array populated with the values from hash h
h.values_at(key1, key2)
# Return an array containing the values associated with the given keys key1 and key2 of hash h

# General I
h1.eql?(h2)
# Return true if h1 and h2 are both hashes with the same content
h.flatten
# Return a new array that is a one-dimensional flattening of hash h
h.invert
# Return a new hash created by using hash h's values as keys, and the keys as values
h1.merge(h2)
# Return a new hash containing the contents of h1 and h2 (use an optional block to solve conflicts)
h1.merge!(h2)
# Add the contents of h2 to h1 (use an optional block to solve conflicts)
h.shift
# Remove a key-value pair from hash h and return it as the two item array [key,value]
h.size
# Return the number of key-value pairs in hash h (option 2)
h.to_a
# Convert hash h to a nested array of [key,value] arrays

# General II
h.assoc(obj)
# Search through hash h comparing obj with each key and return the key-value pair as a two element array
h.compare_by_identity
# Make hash h compare its keys by their identity (exact same objects)
h.compare_by_identity?
# Return true if hash h will compare its keys by identity
h.hash
# Compute a hash-code for hash h
h.to_s
# Return the contents of hash h as string
h.rassoc(obj)
# Search through the hash comparing obj with the values of hash h. Return first k-v pair (two element array) that matches
h.rehash
# Rebuild hash h based on the current hash values for each key