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https://github.com/lazychaser/laravel-nestedset

Effective tree structures in Laravel 4-8
https://github.com/lazychaser/laravel-nestedset

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Effective tree structures in Laravel 4-8

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README 

        
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This is a Laravel 4-10 package for working with trees in relational databases.



*   **Laravel 11.0** is supported since v6.0.4

*   **Laravel 10.0** is supported since v6.0.2

*   **Laravel 9.0** is supported since v6.0.1

*   **Laravel 8.0** is supported since v6.0.0

*   **Laravel 5.7, 5.8, 6.0, 7.0** is supported since v5

*   **Laravel 5.5, 5.6** is supported since v4.3

*   **Laravel 5.2, 5.3, 5.4** is supported since v4

*   **Laravel 5.1** is supported in v3

*   **Laravel 4** is supported in v2



__Contents:__



- [Theory](#what-are-nested-sets)

- [Documentation](#documentation)

    -   [Inserting nodes](#inserting-nodes)

    -   [Retrieving nodes](#retrieving-nodes)

    -   [Deleting nodes](#deleting-nodes)

    -   [Consistency checking & fixing](#checking-consistency)

    -   [Scoping](#scoping)

- [Requirements](#requirements)

- [Installation](#installation)



What are nested sets?

---------------------



Nested sets or [Nested Set Model](http://en.wikipedia.org/wiki/Nested_set_model) is

a way to effectively store hierarchical data in a relational table. From wikipedia:



> The nested set model is to number the nodes according to a tree traversal,

> which visits each node twice, assigning numbers in the order of visiting, and

> at both visits. This leaves two numbers for each node, which are stored as two

> attributes. Querying becomes inexpensive: hierarchy membership can be tested by

> comparing these numbers. Updating requires renumbering and is therefore expensive.



### Applications



NSM shows good performance when tree is updated rarely. It is tuned to be fast for

getting related nodes. It'is ideally suited for building multi-depth menu or

categories for shop.



Documentation

-------------



Suppose that we have a model `Category`; a `$node` variable is an instance of that model

and the node that we are manipulating. It can be a fresh model or one from database.



### Relationships



Node has following relationships that are fully functional and can be eagerly loaded:



-   Node belongs to `parent`

-   Node has many `children`

-   Node has many `ancestors`

-   Node has many `descendants`



### Inserting nodes



Moving and inserting nodes includes several database queries, so it is

highly recommended to use transactions.



__IMPORTANT!__ As of v4.2.0 transaction is not automatically started



Another important note is that __structural manipulations are deferred__ until you

hit `save` on model (some methods implicitly call `save` and return boolean result

of the operation).



If model is successfully saved it doesn't mean that node was moved. If your application

depends on whether the node has actually changed its position, use `hasMoved` method:



```php

if ($node->save()) {

    $moved = $node->hasMoved();

}

```



#### Creating nodes



When you simply creating a node, it will be appended to the end of the tree:



```php

Category::create($attributes); // Saved as root

```



```php

$node = new Category($attributes);

$node->save(); // Saved as root

```



In this case the node is considered a _root_ which means that it doesn't have a parent.



#### Making a root from existing node



```php

// #1 Implicit save

$node->saveAsRoot();



// #2 Explicit save

$node->makeRoot()->save();

```



The node will be appended to the end of the tree.



#### Appending and prepending to the specified parent



If you want to make node a child of other node, you can make it last or first child.



*In following examples, `$parent` is some existing node.*



There are few ways to append a node:



```php

// #1 Using deferred insert

$node->appendToNode($parent)->save();



// #2 Using parent node

$parent->appendNode($node);



// #3 Using parent's children relationship

$parent->children()->create($attributes);



// #5 Using node's parent relationship

$node->parent()->associate($parent)->save();



// #6 Using the parent attribute

$node->parent_id = $parent->id;

$node->save();



// #7 Using static method

Category::create($attributes, $parent);

```



And only a couple ways to prepend:



```php

// #1

$node->prependToNode($parent)->save();



// #2

$parent->prependNode($node);

```



#### Inserting before or after specified node



You can make `$node` to be a neighbor of the `$neighbor` node using following methods:



*`$neighbor` must exists, target node can be fresh. If target node exists,

it will be moved to the new position and parent will be changed if it's required.*



```php

# Explicit save

$node->afterNode($neighbor)->save();

$node->beforeNode($neighbor)->save();



# Implicit save

$node->insertAfterNode($neighbor);

$node->insertBeforeNode($neighbor);

```



#### Building a tree from array



When using static method `create` on node, it checks whether attributes contains

`children` key. If it does, it creates more nodes recursively.



```php

$node = Category::create([

    'name' => 'Foo',



    'children' => [

        [

            'name' => 'Bar',



            'children' => [

                [ 'name' => 'Baz' ],

            ],

        ],

    ],

]);

```



`$node->children` now contains a list of created child nodes.



#### Rebuilding a tree from array



You can easily rebuild a tree. This is useful for mass-changing the structure of

the tree.



```php

Category::rebuildTree($data, $delete);

```



`$data` is an array of nodes:



```php

$data = [

    [ 'id' => 1, 'name' => 'foo', 'children' => [ ... ] ],

    [ 'name' => 'bar' ],

];

```



There is an id specified for node with the name of `foo` which means that existing

node will be filled and saved. If node is not exists `ModelNotFoundException` is

thrown. Also, this node has `children` specified which is also an array of nodes;

they will be processed in the same manner and saved as children of node `foo`.



Node `bar` has no primary key specified, so it will be created.



`$delete` shows whether to delete nodes that are already exists but not present

in `$data`. By default, nodes aren't deleted.



##### Rebuilding a subtree



As of 4.2.8 you can rebuild a subtree:



```php

Category::rebuildSubtree($root, $data);

```



This constraints tree rebuilding to descendants of `$root` node.



### Retrieving nodes



*In some cases we will use an `$id` variable which is an id of the target node.*



#### Ancestors and descendants



Ancestors make a chain of parents to the node. Helpful for displaying breadcrumbs

to the current category.



Descendants are all nodes in a sub tree, i.e. children of node, children of

children, etc.



Both ancestors and descendants can be eagerly loaded.



```php

// Accessing ancestors

$node->ancestors;



// Accessing descendants

$node->descendants;

```



It is possible to load ancestors and descendants using custom query:



```php

$result = Category::ancestorsOf($id);

$result = Category::ancestorsAndSelf($id);

$result = Category::descendantsOf($id);

$result = Category::descendantsAndSelf($id);

```



In most cases, you need your ancestors to be ordered by the level:



```php

$result = Category::defaultOrder()->ancestorsOf($id);

```



A collection of ancestors can be eagerly loaded:



```php

$categories = Category::with('ancestors')->paginate(30);



// in view for breadcrumbs:

@foreach($categories as $i => $category)

    {{ $category->ancestors->count() ? implode(' > ', $category->ancestors->pluck('name')->toArray()) : 'Top Level' }}


    {{ $category->name }}

@endforeach

```



#### Siblings



Siblings are nodes that have same parent.



```php

$result = $node->getSiblings();



$result = $node->siblings()->get();

```



To get only next siblings:



```php

// Get a sibling that is immediately after the node

$result = $node->getNextSibling();



// Get all siblings that are after the node

$result = $node->getNextSiblings();



// Get all siblings using a query

$result = $node->nextSiblings()->get();

```



To get previous siblings:



```php

// Get a sibling that is immediately before the node

$result = $node->getPrevSibling();



// Get all siblings that are before the node

$result = $node->getPrevSiblings();



// Get all siblings using a query

$result = $node->prevSiblings()->get();

```



#### Getting related models from other table



Imagine that each category `has many` goods. I.e. `HasMany` relationship is established.

How can you get all goods of `$category` and every its descendant? Easy!



```php

// Get ids of descendants

$categories = $category->descendants()->pluck('id');



// Include the id of category itself

$categories[] = $category->getKey();



// Get goods

$goods = Goods::whereIn('category_id', $categories)->get();

```



#### Including node depth



If you need to know at which level the node is:



```php

$result = Category::withDepth()->find($id);



$depth = $result->depth;

```



Root node will be at level 0. Children of root nodes will have a level of 1, etc.



To get nodes of specified level, you can apply `having` constraint:



```php

$result = Category::withDepth()->having('depth', '=', 1)->get();

```



__IMPORTANT!__ This will not work in database strict mode



#### Default order



All nodes are strictly organized internally. By default, no order is

applied, so nodes may appear in random order and this doesn't affect

displaying a tree. You can order nodes by alphabet or other index.



But in some cases hierarchical order is essential. It is required for

retrieving ancestors and can be used to order menu items.



To apply tree order `defaultOrder` method is used:



```php

$result = Category::defaultOrder()->get();

```



You can get nodes in reversed order:



```php

$result = Category::reversed()->get();

```



To shift node up or down inside parent to affect default order:



```php

$bool = $node->down();

$bool = $node->up();



// Shift node by 3 siblings

$bool = $node->down(3);

```



The result of the operation is boolean value of whether the node has changed its

position.



#### Constraints



Various constraints that can be applied to the query builder:



-   __whereIsRoot()__ to get only root nodes;

-   __hasParent()__ to get non-root nodes;

-   __whereIsLeaf()__ to get only leaves;

-   __hasChildren()__ to get non-leave nodes;

-   __whereIsAfter($id)__ to get every node (not just siblings) that are after a node

    with specified id;

-   __whereIsBefore($id)__ to get every node that is before a node with specified id.



Descendants constraints:



```php

$result = Category::whereDescendantOf($node)->get();

$result = Category::whereNotDescendantOf($node)->get();

$result = Category::orWhereDescendantOf($node)->get();

$result = Category::orWhereNotDescendantOf($node)->get();

$result = Category::whereDescendantAndSelf($id)->get();



// Include target node into result set

$result = Category::whereDescendantOrSelf($node)->get();

```



Ancestor constraints:



```php

$result = Category::whereAncestorOf($node)->get();

$result = Category::whereAncestorOrSelf($id)->get();

```



`$node` can be either a primary key of the model or model instance.



#### Building a tree



After getting a set of nodes, you can convert it to tree. For example:



```php

$tree = Category::get()->toTree();

```



This will fill `parent` and `children` relationships on every node in the set and

you can render a tree using recursive algorithm:



```php

$nodes = Category::get()->toTree();



$traverse = function ($categories, $prefix = '-') use (&$traverse) {

    foreach ($categories as $category) {

        echo PHP_EOL.$prefix.' '.$category->name;



        $traverse($category->children, $prefix.'-');

    }

};



$traverse($nodes);

```



This will output something like this:



```

- Root

-- Child 1

--- Sub child 1

-- Child 2

- Another root

```



##### Building flat tree



Also, you can build a flat tree: a list of nodes where child nodes are immediately

after parent node. This is helpful when you get nodes with custom order

(i.e. alphabetically) and don't want to use recursion to iterate over your nodes.



```php

$nodes = Category::get()->toFlatTree();

```



Previous example will output:



```

Root

Child 1

Sub child 1

Child 2

Another root

```



##### Getting a subtree



Sometimes you don't need whole tree to be loaded and just some subtree of specific node.

It is show in following example:



```php

$root = Category::descendantsAndSelf($rootId)->toTree()->first();

```



In a single query we are getting a root of a subtree and all of its

descendants that are accessible via `children` relation.



If you don't need `$root` node itself, do following instead:



```php

$tree = Category::descendantsOf($rootId)->toTree($rootId);

```



### Deleting nodes



To delete a node:



```php

$node->delete();

```



**IMPORTANT!** Any descendant that node has will also be deleted!



**IMPORTANT!** Nodes are required to be deleted as models, **don't** try do delete them using a query like so:



```php

Category::where('id', '=', $id)->delete();

```



This will break the tree!



`SoftDeletes` trait is supported, also on model level.



### Helper methods



To check if node is a descendant of other node:



```php

$bool = $node->isDescendantOf($parent);

```



To check whether the node is a root:



```php

$bool = $node->isRoot();

```



Other checks:



*   `$node->isChildOf($other);`

*   `$node->isAncestorOf($other);`

*   `$node->isSiblingOf($other);`

*   `$node->isLeaf()`



### Checking consistency



You can check whether a tree is broken (i.e. has some structural errors):



```php

$bool = Category::isBroken();

```



It is possible to get error statistics:



```php

$data = Category::countErrors();

```



It will return an array with following keys:



-   `oddness` -- the number of nodes that have wrong set of `lft` and `rgt` values

-   `duplicates` -- the number of nodes that have same `lft` or `rgt` values

-   `wrong_parent` -- the number of nodes that have invalid `parent_id` value that

    doesn't correspond to `lft` and `rgt` values

-   `missing_parent` -- the number of nodes that have `parent_id` pointing to

    node that doesn't exists



#### Fixing tree



Since v3.1 tree can now be fixed. Using inheritance info from `parent_id` column,

proper `_lft` and `_rgt` values are set for every node.



```php

Node::fixTree();

```



### Scoping



Imagine you have `Menu` model and `MenuItems`. There is a one-to-many relationship

set up between these models. `MenuItem` has `menu_id` attribute for joining models

together. `MenuItem` incorporates nested sets. It is obvious that you would want to

process each tree separately based on `menu_id` attribute. In order to do so, you

need to specify this attribute as scope attribute:



```php

protected function getScopeAttributes()

{

    return [ 'menu_id' ];

}

```



But now, in order to execute some custom query, you need to provide attributes

that are used for scoping:



```php

MenuItem::scoped([ 'menu_id' => 5 ])->withDepth()->get(); // OK

MenuItem::descendantsOf($id)->get(); // WRONG: returns nodes from other scope

MenuItem::scoped([ 'menu_id' => 5 ])->fixTree(); // OK

```



When requesting nodes using model instance, scopes applied automatically based

on the attributes of that model:



```php

$node = MenuItem::findOrFail($id);



$node->siblings()->withDepth()->get(); // OK

```



To get scoped query builder using instance:



```php

$node->newScopedQuery();

```



#### Scoping and eager loading



Always use scoped query when eager loading:



```php

MenuItem::scoped([ 'menu_id' => 5])->with('descendants')->findOrFail($id); // OK

MenuItem::with('descendants')->findOrFail($id); // WRONG

```



Requirements

------------



- PHP >= 5.4

- Laravel >= 4.1



It is highly suggested to use database that supports transactions (like MySql's InnoDb)

to secure a tree from possible corruption.



Installation

------------



To install the package, in terminal:



```

composer require kalnoy/nestedset

```



### Setting up from scratch



#### The schema



For Laravel 5.5 and above users:



```php

Schema::create('table', function (Blueprint $table) {

    ...

    $table->nestedSet();

});



// To drop columns

Schema::table('table', function (Blueprint $table) {

    $table->dropNestedSet();

});

```



For prior Laravel versions:



```php

...

use Kalnoy\Nestedset\NestedSet;



Schema::create('table', function (Blueprint $table) {

    ...

    NestedSet::columns($table);

});

```



To drop columns:



```php

...

use Kalnoy\Nestedset\NestedSet;



Schema::table('table', function (Blueprint $table) {

    NestedSet::dropColumns($table);

});

```



#### The model



Your model should use `Kalnoy\Nestedset\NodeTrait` trait to enable nested sets:



```php

use Kalnoy\Nestedset\NodeTrait;



class Foo extends Model {

    use NodeTrait;

}

```



### Migrating existing data



#### Migrating from other nested set extension



If your previous extension used different set of columns, you just need to override

following methods on your model class:



```php

public function getLftName()

{

    return 'left';

}



public function getRgtName()

{

    return 'right';

}



public function getParentIdName()

{

    return 'parent';

}



// Specify parent id attribute mutator

public function setParentAttribute($value)

{

    $this->setParentIdAttribute($value);

}

```



#### Migrating from basic parentage info



If your tree contains `parent_id` info, you need to add two columns to your schema:



```php

$table->unsignedInteger('_lft');

$table->unsignedInteger('_rgt');

```



After [setting up your model](#the-model) you only need to fix the tree to fill

`_lft` and `_rgt` columns:



```php

MyModel::fixTree();

```



License

=======



Copyright (c) 2017 Alexander Kalnoy



Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:



The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.



THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.