Query scope in Laravel is a very important feature that allows you to define some commonly used query methods in the model for reuse throughout the entire application. These query scopes can be global (apply to the entire model) or local (apply only to a method of the model).

In this article, we will introduce the definition, use and some things that should be paid attention to the query scope in Laravel.

1. Definition of query scope

Query scope is an anonymous function that receives a $query parameter, which is an Eloquent query builder instance. In this anonymous function, you can perform some query operations on the instance, such as adding where clauses, order by clauses, etc.

The following is a basic query scope definition example:

public function scopePublished($query)
{
    return $query->where('status', '=', 'published');
}

In the above example, we define a query scope named published, which will automatically add a query scope when querying where clause to filter published models.

2. Using query scope

Using query scope is very simple, just call the corresponding method of the model. For example, if we use the published query scope in the above example, we only need to call the following code:

$posts = Post::published()->get();

The above code will return a collection of all published Post instances.

If you need to pass parameters into the query scope, just add parameters in this method. For example:

public function scopeCategory($query, $categoryId)
{
    return $query->where('category_id', '=', $categoryId);
}

This query scope can be used to filter blog posts in a specific category.

$posts = Post::category(1)->get();

The above code will return all blog posts with category ID 1.

Note: Query scopes can be chained, so you can use multiple query scopes at the same time to obtain more precise results.

3. Global definition of query scope

If you want to use the same query scope throughout the model, you can define a global query scope. To do this, simply call the boot method in your model and define a global query scope using the static::addGlobalScope method.

The following is a basic global query scope example:

protected static function boot()
{
    parent::boot();

    static::addGlobalScope('active', function (Builder $builder) {
        $builder->where('active', '=', 1);
    });
}

In the above example, we define a global query scope named active and limit it to the active field equal to 1 record.

Now, when you query the model in any method, the query scope will automatically take effect.

4. Remove query scope

Sometimes we may need to remove the query scope of a specific model. Laravel provides the removeGlobalScope method to help us achieve this.

For example, assuming we have a global query scope named active, we can use the following method to remove it:

$users = User::withoutGlobalScope('active')->get();

The above code will return all queries that are not restricted by the active scope user.

Note: If you want to remove all global query scopes, you can use the withoutGlobalScopes method.

$users = User::withoutGlobalScopes()->get();

The above code will return all users not restricted by any global query scope.

Summary

Query scope is an extremely powerful feature in Laravel. By using query scopes, you can easily reuse common query operations throughout your application and organize your code more clearly. Learning the correct use of query scopes can not only improve your productivity, but also help you build more robust applications.

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