[Rails] Different find methods

Summary

find

• Usually use id to search

• Can also return an array

# find by id
Person.find(1)       # returns the object for ID = 1
Person.find(1, 2, 6) # returns an array for objects with IDs in (1, 2, 6)
Person.find([7, 17]) # returns an array for objects with IDs in (7, 17)
Person.find([1])     # returns an array for the object with ID = 1
Person.find(1, :conditions => "administrator = 1", :order => "created_on DESC")

• Raises ActiveRecord::RecordNotFound if not found

find_by

• Only returns the first found record
• So make sure the field to look up is unique

• find_by only returns nil if not found
• You can use find_by!

Post.find_by name: 'Spartacus', rating: 4
Post.find_by "published_at < ?", 2.weeks.ago

find_by_field

• Dynamic finder; crazy Rails magic…

• find_by_field(value) is pretty much find_by(field: value)

Source