bang methods

bang.rb

# Bang method behavior: upcase!

email = "[email protected]"
# Upcasing a string, but not changing the variable email's value
email.upcase
#  => "[email protected]"
email
# => "[email protected]"

# Using bang to upcase a string
email.upcase!
#  => "[email protected]"
email
#  => "[email protected]"

# ⚠️ Now look at this weird behavior with !upcase:
# As email is already upcased...
email.upcase!
# => nil

# It returns nil... if it didn't need to change it. 😵‍💫

# On Ruby on Rails, we have the find_by and find_by! methods
# find_by! raises an exception when it can't find a record.

# Wrapping up: bang methods are about all about warning the developer
# that the new method behavior differs from its other version.