Eloquent Back

• Eloquent is the 'Object Relational Mapping'(ORM) in Laravel. We can easily handle data by using Eloquent Class.

<?php

class Article extends Eloquent {
    protected $fillable = [];
}

1. Base Operation

• When extending the class Eloquent, we can use many methods to handle data like first(), find(), where() or orderBy().
• There is some case to know how to use Eloquent to handle data:

Case1: find the article which id is 2 and print out its title

$article = Article::find(2);

echo $article->title;

Case2: find out the article which title is 'hello' and print out its id

$article = Article::where('title', 'hello')->first();

echo $article->id;

Case3: print out titles of all articles

$articles = Article::all();

foreach ($articles as $key) {
    echo $key->title;
}

Case4: print out titles of articles which id is between 10 and 20

$articles = Article::where('id', '>=', 10)->where('id', '<=', 20)->get();

foreach ($articles as $key) {
    echo $key->title;
}

Case5: print out titles of all articles under the order of ‘update_at'

$articles = Article::orderBy('update_at', 'desc')->get();

foreach ($articles as $key) {
    echo $key->title;
}

2. Builder

• Builder is used to complete the function of chaining operation:

/** the follow sentence will return a builder which can continue to add conditions */
Article::where('id', 1)

• the path of builder is in Illuminate\Database\Eloquent\Builder

3. Relationships

• Relationships mean the relationships between two models.
  • One to One
  • One to Many
  • Many to Many

One to One

user: id ... ... account_id
account: id ... ... user_id

• If we want to query related info in the table Account, we will have the following model of User:

<?php

class User extends Eloquent {
    protected $table = 'users';

    public function hasOneAccount()
    {
        return $this->hasOne('Account', 'user_id', 'id');
    }
}

• and then, we can query the account which user id is 10:

/** SQL: select * from account where user_id = 10; */
$account = User::find(10)->hasOneAccount;

• the related model of Account should be as follow:

<?php

class Account extends Eloquent {
    protected $table = 'accounts';

    public function belongsToUser()
    {
        return $this->belongsTo('User', 'user_id', 'id');
    }
}

One to Many

user: id ... ...
pay: id ... ... user_id

• the model of User should be:

<?php

class User extends Eloquent {
    protected $table = 'users';

    public function hasManyPays()
    {
        return $this->hasMany('Pay', 'user_id', 'id');
    }
}

• and the model of Pay should be as follow:

<?php

class Pay extends Eloquent {
    protected $table = 'pays';

    public function belongsToUser()
    {
        return $this->belongsTo('User', 'user_id', 'id');   
    }
}

• then we can query like this:

/** SQL: select * from pays where user_id = 10; */
$accounts = User::find(10)->hasManyPays()->get();

/** If you want to show out all two tables */
$accounts = User::where('id', 10)->with('hasManyPays')->first();
/** then you can look fr the data of another table */
var_dump($accounts->hasManyPays->pay_info);

Many to Many

article: id ... ...
tag: id ... ...
article_tag: article_id tag_id

• the model will be:

class Tag extends Eloquent {
    protected $table = 'tags';

    public function belongsToManyArticle()
    {
        return $this->belongsToMany('Article', 'article_tag', 'tag_id', 'article_id');
    }
}

• the query will be:

$tagsWithArticles = Tag::take(10)->get()->belongsToManyArticle()->get();

4. Eager Loading

• You'll find that if you want to query 10 users with info in the table, Account, you are in need to use 1 + 10 SQL sentences. Nevertheless, you'll only use 1 + 1 instead when using Eager Loading. More details about Eager Loading in http://laravel-china.org/docs/eloquent#eager-loading.

/** SQL: select * from account wher id in (1, 2, 3, ...) */
$users = User::with('hasOneAccount')->take(10)->get();

5. Specific Attributes

/** Key and Value */
$tagsName = Tag::select('name')->get();

/** Only Value */
$tagsNameValue = Tag::pluck('name');

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