Cheat sheets of Ruby-on-Rails methods (Model and Relation; Rails 5.2)

rails_method_cheat_sheets.md

% Ruby-on-Rails method cheat sheets

Optimised for pandoc flavour, but works more or less on Github flavour.

Relations instance methods and Model class methods

The table summarises the instance methods of Relations, which can be used as class methods of Methods, and their returned values (self means a Relation instance, even when it is run as a class method of a Model). Several instance methods of Model instances that do similar operations are also included.

Relation-methods	Model-instance	self	Array	Model	Bool	Else	Note
all		✔
any?					✔
average(Sym)						Object
count						Integer
create(Hash)				✔
create_with(Hash)		✔
	destroy			✔
destroy_all				✔
distinct(set=true)		✔
eager_load(*Syms)		✔
entries			✔
exists?(*Int)					✔
extending(*modu, &bl)		✔
explain						String
find(*Int)			✔	✔
find_by(Hash)				✔
find_by!(Hash)				✔
find_each(&b)				✔
find_or_create_by(Hash,&b)				✔
find_or_initialize_by				✔
find_by_sql(SQL,*Arr)			✔
first(Int)			✔	✔
first_or_initialize				✔
forty_two				✔
from(Table,sub-index)		✔
group(String)		✔
having(String)		✔
	id					Integer
ids			✔
includes(*Obj)		✔
joins(*Obj)		✔
last(Int)			✔
left_outer_joins		✔
limit(Int)		✔
lock(true)		✔
lock!(true)	✔	✔					Row-based
locked?					✔
locking_enabled?	✔				✔
	lock_optimistically				✔
	lock_optimistically?				✔
	with_lock(&bloc)						Row-based
many?					✔
maximum(Sym)						Object
minimum(Sym)						Object
new(*Hash)				✔
none		✔				(Empty)
offset(Int)		✔
only(*Sym)		✔
or(other)		✔
order(Sym,Hs)		✔
pluck(Sym)			✔
preload(*Sym)		✔
readonly		✔
references(*tb_names)		✔
reorder(*)		✔
reverse_order		✔
rewhere(*)		✔
select(*Sym)		✔
select_all(Str)		✔
unscope(*Sym)		✔
	update(Hash)			✔
update_all(String)
take				✔
take(Int)			✔
transaction(&bloc)
where(Hash/*Arr)		✔

: Summary of Relation instance methods

Model instance methods

Suppose the DB table has a column name called mycol.

Model methods	self	Hash	Array	Bool	Else	Note
attribute_changed?(Sym)				✔
attribute_changed_in_place?(Sym)				✔
attribute_in_database(Sym)					Object
attribute_names			✔
attributes		✔				{str => Object}
attributes=
attributes_in_database		✔				Alias: changed_attributes
changed			✔			changed_attributes.keys
changed?				✔		Any unsaved changes exist?
changed_attributes		✔				original values of unsaved
changed_attribute_names_to_save			✔			Alias: changed
changes		✔				{str=>[bef, aft]} unsaved
changes_to_save		✔				Alias: changes
destroyed?				✔
errors					Errors	cf errors.details[:mycol]
has_attribute?(Sym)				✔
has_changes_to_save?				✔		Alias: changed?
new_record?				✔
persisted?				✔		neither new nor destroyed?
previous_changes		✔				Before/After save
restore_attributes						Undo the unsaved changes
saved_changes			✔			of Hash=>Array, just saved
saved_changes?				✔		!saved_changes.empty?
created_at					Time
id					Integer
type
updated_at					Time
mycol					Object
mycol=					Object
mycol?				✔
mycol_before_last_save					Object
mycol_before_type_cast					Object
mycol_came_from_user?				✔
mycol_change			✔
mycol_change_to_be_saved			✔
mycol_changed?				✔
mycol_in_database					Object
mycol_previous_change			✔
mycol_previously_changed?				✔
mycol_was					Object
mycol_will_change!
restore_mycol!
saved_change_to_mycol			✔
saved_change_to_mycol?				✔
will_save_change_to_mycol?				✔
becomes(Klass)	✔
delete	✔					Avoids callbacks
destroy				✔		Returned frozen
decrement(Sym, by=1)	✔					Skip validation
increment(Sym, by=1)	✔					Skip validation
reload	✔
save(validate: true)				✔
save!(touch: true)	✔					Exception if fails
toggle(Sym)	✔					Toggles Boolean value
touch(*Syms, time: nil)
update(Hash)	✔					m.a=X; m.save
update!(Hash)	✔					m.a=X; m.save!
update_attribute(Sym,Obj)						No validation but callbacks
update_attributes(Hash)
update_attributes!(Hash)
update_columns(Hash)						Direct SQL call
valid?				✔		!invalid?

: Model insntance methods and its returns