Here’s a complete answer to this issue, in case people visiting this question are new to Ruby on Rails and having a hard time putting everything together (as I was when I first looked into this). Some parts of the solution take place in your Migrations and some in your Models: Migrations class CreatePrivateMessages < … Read more
Chriss I hope this simple example helps. Guess you have a Java class public class A { private B b; … } In UML you would model this relationship as an association from A to B: A -> B with the following modeling elements: Class B Class A + Property b : B [0..1] (owned … Read more
Please read Routing Explicit Joins/Statements into Eagerly Loaded Collections. Then using contains_eager you can structure your query and get exactly what you want: authors = ( session.query(Author) .join(Author.books) .options(contains_eager(Author.books)) # tell SA that we load “all” books for Authors .filter(Book.title.like(‘%SQL%’)) ).all() Please note that you are actually tricking sqlalchemy into thinking that it has loaded … Read more
m:n is used to denote a many-to-many relationship (m objects on the other side related to n on the other) while 1:n refers to a one-to-many relationship (1 object on the other side related to n on the other).
There’s nothing inherently wrong with having a many-to-many relationship, you’ll just need to create a Junction Table (which is what it sounds like you’re referring to with articlesTags) to facilitate that relationship.
It is possible to extend the relation with query functions: <?php public function comments() { return $this->hasMany(‘Comment’)->orderBy(‘column’); } [edit after comment] <?php class User { public function comments() { return $this->hasMany(‘Comment’); } } class Controller { public function index() { $column = Input::get(‘orderBy’, ‘defaultColumn’); $comments = User::find(1)->comments()->orderBy($column)->get(); // use $comments in the template } } … Read more
Composition final class Car { private final Engine engine; Car(EngineSpecs specs) { engine = new Engine(specs); } void move() { engine.work(); } } Aggregation final class Car { private Engine engine; void setEngine(Engine engine) { this.engine = engine; } void move() { if (engine != null) engine.work(); } } In the case of composition, the … Read more
With with() is for eager loading. That basically means, along the main model, Laravel will preload the relationship(s) you specify. This is especially helpful if you have a collection of models and you want to load a relation for all of them. Because with eager loading you run only one additional DB query instead of … Read more
One-to-one: Use a foreign key to the referenced table: student: student_id, first_name, last_name, address_id address: address_id, address, city, zipcode, student_id # you can have a # “link back” if you need You must also put a unique constraint on the foreign key column (addess.student_id) to prevent multiple rows in the child table (address) from relating … Read more