Laravel雄辩地说出了多对多关系决定了是否存在关系

Question

I am working on a project with many-to-many relationship between two tables roles and users. I also have a pivot table role_user that holds information about the relation between the other two tables.

role_user two fields namely the ids of the two tables: role_id and user_id.

Now I have a user object gotten from the users table and another role object gotten from the roles table. I want to determine if a particular role belongs to a certain user.

I know this can be done by creating a model for the pivot table and then using the model, the role_user table can be queried and determined if the relation exists. But I find this method stressful and wonder if eloquent provides an easy method to determine this. Thanks for any help?

Answer 1

You don't need to have a role_user model. You might already have role model and the user model related to the tables you have. Specify the many to many relationship in Role.php and User.php

User.php - function roles

    public function roles()
{
    return $this->belongsToMany('App\Role');
}

Role.php - function users

    public function users()
{
    return $this->belongsToMany('App\User');
}

You may have to define other parameters like pivot table etc if you don't follow the naming conventions in table columns and tables. Since you seem to have follow the rules I'm not going to explain it. But you always can refer to laravel documentation's eloquent many-to-may section

now you can easily check whether a user belongs to a certain role. Consider the following examle

    //select a user 
    $user = App\User::find(1);
    //select a role
    $role = App\Role::find(1);
    //get $user's roles. This ill return an array of role objects that are belong to $user
    $userRoles = $user->roles;
    //check whether $role is in that array
    if(in_array($role, $userRoles)){
    //do something
    }