Ruby

Basics

@object.methods # returns a list of all methods available on this object
 
# "and" and "&&" are the same
thing1 and thing2
thing1 && thing2
 
# "or" and "||" are the same
thing1 or thing2
thing1 || thing2
 
# Loop a certain number of times with #times
5.times do
  puts "Hello, world!"
end
#=> Alternative fact number 0
#=> Alternative fact number 1
#=> Alternative fact number 2
#=> Alternative fact number 3
#=> Alternative fact number 4

Object equality

#eql? checks both the value type and the actual value it holds.
 
5.eql?(5.0) #=> false; although they are the same value, one is an integer and the other is a float
5.eql?(5)   #=> true
 
#equal? checks whether both values are the exact same object in memory.
 
a = 5
b = 5
a.equal?(b) #=> true

Arrays

# Adding arrays concatenates
a = [1, 2, 3]
b = [3, 4, 5]
 
a + b         #=> [1, 2, 3, 3, 4, 5]
a.concat(b)   #=> [1, 2, 3, 3, 4, 5]
 
# Subtracting arrays returns a copy of the first array,
# removing any values from the second array
[1, 1, 1, 2, 2, 3, 4] - [1, 4]  #=> [2, 2, 3]

Hashes

A hash is like a dictionary where the keys and values can be different.

# Any old key and value type
hash = { 9 => "nine", :six => 6 }
 
# Accessing values in a hash
shoes = {
  "summer" => "sandals",
  "winter" => "boots"
}
 
shoes["summer"]   #=> "sandals"
 
# Adding/changing values
shoes["fall"] = "sneakers"
shoes     #=> {"summer"=>"sandals", "winter"=>"boots", "fall"=>"sneakers"}
 
shoes["summer"] = "flip-flops"
shoes     #=> {"summer"=>"flip-flops", "winter"=>"boots", "fall"=>"sneakers"}
 
# Removing values
shoes.delete("summer")    #=> "flip-flops"
shoes                     #=> {"winter"=>"boots", "fall"=>"sneakers"}
 
# Merging hashes
hash1 = { "a" => 100, "b" => 200 }
hash2 = { "b" => 254, "c" => 300 }
# Duplicated keys will result in the value from the hash on the right remaining
hash1.merge(hash2)      #=> { "a" => 100, "b" => 254, "c" => 300 }
 
# Symbols as hash keys
# 'Rocket' syntax
american_cars = {
  :chevrolet => "Corvette",
  :ford => "Mustang",
  :dodge => "Ram"
}
# 'Symbols' syntax
japanese_cars = {
  honda: "Accord",
  toyota: "Corolla",
  nissan: "Altima"
}
 
# Accessing a hash with symbol keys
american_cars[:ford]    #=> "Mustang"
japanese_cars[:honda]   #=> "Accord"

Ruby QuickRef | zenspider.com | by ryan davis

https://stackoverflow.com/questions/10173097/rails-rspec-difference-between-let-and-let

Local debugging

bundle exec rails console opens a REPL

Then we can do stuff like

${entityName}.all to run a select * from ${entityName}

${entityName}.count to run a select COUNT(*) from ${entityName}