CRUD

Create
Combination of object creation and insertion into database.
Post.create(name: "Granite Rocks!", body: "Check this out.") # Set attributes and call save
Post.create!(name: "Granite Rocks!", body: "Check this out.") # Set attributes and call save!. Will throw an exception when the save failed
Insert
Inserts an already created object into the database.
post = Post.new
post.name = "Granite Rocks!"
post.body = "Check this out."
post.save
​
post = Post.new
post.name = "Granite Rocks!"
post.body = "Check this out."
post.save! # raises when save failed
Read
find
Finds the record with the given primary key.
post = Post.find 1
if post
  puts post.name
end
​
post = Post.find! 1 # raises when no records found
find_by
Finds the record(s) that match the given criteria
post = Post.find_by(slug: "example_slug")
if post
  puts post.name
end
​
post = Post.find_by!(slug: "foo") # raises when no records found.
other_post = Post.find_by(slug: "foo", type: "bar") # Also works for multiple arguments.
first
Returns the first record.
post = Post.first
if post
  puts post.name
end
​
post = Post.first! # raises when no records exist
where, order, limit, offset, group_by
See querying for more details of using the QueryBuilder.
all
Returns all records of a model.
posts = Post.all
if posts
  posts.each do |post|
    puts post.name
  end
end
See querying for more details on using all
Update
Updates a given record already saved in the database.
post = Post.find 1
post.name = "Granite Really Rocks!"
post.save
​
post = Post.find 1
post.update(name: "Granite Really Rocks!") # Assigns attributes and calls save
​
post = Post.find 1
post.update!(name: "Granite Really Rocks!") # Assigns attributes and calls save!. Will throw an exception when the save failed
Delete
Delete a specific record.
post = Post.find 1
post.destroy if post
puts "deleted" if post.destroyed?
​
post = Post.find 1
post.destroy! # raises when delete failed
Clear all records of a model
Post.clear #truncate the table
Migrations
Querying
Last updated 2 years ago