如何在这些实体之间建立Laravel关系？

Question

I have three tables in my database: Users, Books, and Reading. The structure of Reading is:

id, user_id, book_id

Now, I need to access to all the books that the user is reading.

First, I would like to know which kind of relationship is, one to many, many to many, Has Many Through, etc. And what do I have to specify in each model? I mean, in the users model hasMany('Reading') or whatever.

I want to access with something like this: Auth::user()->reading()->books()->get() or something similar.

Answer 1

The kind of relationship where one User can be reading several books and one Book can be read by many users is Many-to-Many relationship.

So, to define such a relation in Laravel you should use belongsToMany method:

class User extends Eloquent
{
    function books()
    {
         return $this->belongsToMany("Book", "Reading", "user_id", "book_id");
    }
}

class Book extends Eloquent
{
    function users()
    {
         return $this->belongsToMany("User", "Reading", "book_id", "user_id");
    }
}

$books = Auth::user()->books;

Notice, you don't need to call method ->books() but use a property ->books, otherwise you'd have to call it like Auth::user()->books()->get().