Rails Flashcards
Give a basic rundown of MVC
MVC = Model View Controller
It is to facilitate a Seperation of Concerns
Model -> data, model should have most complexities, keeping the controller simple
View -> UI, how it looks. should not manipulate data in any way, only display it.
Controller -> passing between Model and View. controller should be simple, model should have most complexities
before running a site with a postgres database what do we need to do?
we need to start a postgres service, aka daemon. we can do this like so:
brew services start postgres
how do we create a rails project?
and then what minimal steps do we take to get it running?
we run the command:
- rails new MyFirstProject –database=postgresql*
- rails server*
# creates some database files for your rails project to use (only needed when not using default database)
rake db:create
# to actually apply the changes do this:
rake db:migrate
what ports are reserved by international standards?
everything below 1024, but also there are reserved ports, check this list first:
https://en.wikipedia.org/wiki/List_of_TCP_and_UDP_port_numbers
what does CRUD stand for?
Create
Read
Update
Destroy
how do we create a resource using a rail command?
rails generate scaffold HighScore name:string high_score:integer box_art_url:text
the object name must be singular, rails will pluralise it for database table names and relevent view and controller folder names
when modifying tables, what files should be accessed directly (if conventient) and what should not be touched?
the schema.rb should be left alone and only modified by migrating migration file/s,
the migration file can be created throught rails commands and possibly filled in or modified manually.
what SQL rails commands can be used to return certain rows from a table?
SomeTable.first
SomeTable.last
SomeTable.all
SomeTable.all[n]
SomeTable.find(n)
how do we see what tables exist via postgres console and what columns it has?
[~/RailsProjects/MeetupClone]$ psql postgres
psql (11.5)
Type “help” for help.
postgres=#
postgres=# \c MeetupClone_development
You are now connected to database “MeetupClone_development” as user “lev”.
MeetupClone_development=#
MeetupClone_development=# \dt
List of relations
Schema | Name | Type | Owner
——–+———————-+——-+——-
public | ar_internal_metadata | table | lev
public | categories | table | lev
public | comments | table | lev
public | events | table | lev
public | groups | table | lev
public | schema_migrations | table | lev
public | users | table | lev
(7 rows)
MeetupClone_development=#
MeetupClone_development=# \d users
Table “public.users”
Column | Type | Collation | Nullable | Default
————–+—————————–+———–+———-+———————————–
id | bigint | | not null | nextval(‘users_id_seq’::regclass)
name | character varying | | not null |
email | text | | not null |
location | text | | |
about_me | text | | |
profile_pic | text | | |
sign_up_date | timestamp without time zone | | not null |
event_id | bigint | | |
created_at | timestamp without time zone | | not null |
updated_at | timestamp without time zone | | not null |
group_id | bigint | | |
Indexes:
“users_pkey” PRIMARY KEY, btree (id)
“index_users_on_event_id” btree (event_id)
“index_users_on_group_id” btree (group_id)
Foreign-key constraints:
“fk_rails_cce00833b9” FOREIGN KEY (event_id) REFERENCES events(id)
“fk_rails_f40b3f4da6” FOREIGN KEY (group_id) REFERENCES groups(id)
MeetupClone_development=#
How do we use SQL rails commands to create, update and destroy table rows?
- HighScore.create!(name:”Bubble Bobble”,high_score:420000)*
- HighScore.find(1).update!(high_score: 320000, box_art_url: “https://someurladd.com”)*
- HighScore.find(1).destroy*
how do we use a rails command to select with a conditional?
how do we do it with wild card strings?
- HighScore.where(“high_score > ?”, 3000)*
- HighScore.where(“high_score > ?”, value_variable)*
- HighScore.where(“name like ‘This%’”)*
what are the two syntaxes we can use to generate a migration to add or remove a column from a table?
we can use snake case and camel case
- rails generate migration add_validated_to_high_scores validated:boolean*
- rails generate migration RemoveValidatedFromHighScores validated:boolean*
