This is a Laravel 4 package for working with trees in a database.
Contents:
Nested sets or 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.
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.
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.
Node has two predefined relationships: parent and children. They are fully
functional, except for Laravel's has due to limitations of the framework.
You can use hasChildren or hasParent to apply constraints:
$items = Category::hasChildren()->get();Moving and inserting nodes includes several database queries, so transaction is automatically started when node is saved. It is safe to use global transaction if you work with several models.
Another important note is that structural manipulations are deferred until you
hit save on model (some methods implicitly call save and return boolean result
of the operation).
If model is successfully saved it doesn't mean that node has moved. To check whether
it has, use hasMoved function:
if ($node->save())
{
$moved = $node->hasMoved();
}When you just create a node, it will be appended to the end of the tree:
Category::create($attributes);In this case the node is considered a root which means that it doesn't have a parent.
// #1 Implicit save
$node->saveAsRoot();
// #2 Explicit save
$node->makeRoot()->save();The node will be appended to the end of the tree.
If you want to make node a child of other node, you can make it last or first child.
$parent variable is the node that exists in database, no matter how we get it.
There are few ways to append a node:
// #1 Using deferred insert
$node->appendTo($parent)->save();
// #2 Using parent node
$parent->append($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:
// #1
$node->prependTo($parent)->save();
// #2
$parent->prepend($node);You can make a $node to be a neighbor of the $neighbor node using following methods:
Neighbor is existing node, target node can be fresh. If target node is exists, it will be moved to the new position and parent will be changed if it's needed.
# Explicit save
$node->after($neighbor)->save();
$node->before($neighbor)->save();
# Implicit save
$node->insertAfter($neighbor);
$node->insertBefore($neighbor);$bool = $node->down();
$bool = $node->up();
// Make node lower by 3 siblings
$bool = $node->down(3);When using static method create on node, it checks whether attributes contains
children key. If it does, it creates more nodes recursively.
$node = Category::create(
[
'name' => 'Foo',
'children' =>
[
[
'name' => 'Bar',
'children' =>
[
[ 'name' => 'Baz' ],
],
],
],
]);$node->children now contains a list of created child nodes.
In some cases we will use an $id variable which is an id of the target node.
// #1 Using accessor
$result = $node->getAncestors();
// #2 Using a query
$result = $node->ancestors()->get();
// #3 Getting ancestors by id of the node
$result = Category::ancestorsOf($id);
// #4 Applying constraints
$result = Category::whereAncestorOf($id)->get();// #1 Using accessor
$result = $node->getDescendants();
// #2 Using a query
$result = $node->descendants()->get();
// #3 Getting ancestors by id of the node
$result = Category::descendantsOf($id);
// #4 Applying constraints
$result = Category::whereDescendantOf($id)->get();$result = $node->getSiblings();
$result = $node->siblings()->get();To get just next siblings (default order is applied here):
// 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 (reversed order is applied):
// 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();Imagine that each category has many goods. I.e. HasMany relationship is established.
How can you get all goods of all categories that are descendants of some node? Easy!
// Get ids of descendants
$descendants = $node->descendants()->lists('id');
// Get goods
$goods = Goods::whereIn('category_id', $descendants)->get();You have noticed that some methods return a query builder instance. It has some features.
If you need to know at which level the node is:
$result = Category::withDepth()->find($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:
$result = Category::withDepth()->having('depth', '=', 1)->get();Each node has it's own unique value that determines its position in the tree. If
you want node to be ordered by this value, you can use defaultOrder method on
the query builder:
// All nodes will now be ordered by lft value
$result = Category::defaultOrder()->get();You can get nodes in reversed order:
$result = Category::reversed()->get();- whereIsRoot() to get only root nodes;
- hasChildren() to get nodes that have children;
- hasParent() to get non-root nodes;
- whereIsAfter($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.
To check if node is a descendant of other node:
$bool = $node->isDescendantOf($parent);To check whether the node is root:
$bool = $node->isRoot();You can check whether a tree is broken (i.e. has some structural errors):
$bool = Category::isBroken();It is possible to get error statistics:
$data = Category::countErrors();It will return an array with following keys:
oddness-- the number of nodes that have wrong set oflftandrgtvalues;duplicates-- the number of nodes that have samelftorrgtvalues;wrong_parent-- the number of nodes that have invalidparent_idvalue that doesn't correspond tolftandrgtvalues.
- PHP >= 5.4
- Laravel >= 4.1
Models are extended from new base class rather than Eloquent, so it's not possible
to use another framework that overrides Eloquent.
It is highly suggested to use database that supports transactions (like MySql's InnoDb) to secure a tree from possible corruption.
To install the package, in terminal:
composer require kalnoy/nestedset:~2.0@beta
Add some aliases:
'aliases' => array(
...
'NestedSet' => 'Kalnoy\Nestedset\NestedSet',
'Node' => 'Kalnoy\Nestedset\Node',
),You can use a method to add needed columns with default names:
Schema::create('table', function (Blueprint $table)
{
...
NestedSet::columns($table);
});To drop columns:
Schema::table('table', function (Blueprint $table)
{
NestedSet::dropColumns($table);
});If, for some reasons, you want to init everything by yourself, this is preferred schema:
$table->unsignedInteger('_lft');
$table->unsignedInteger('_rgt');
$table->unsignedInteger('parent_id')->nullable();You can change names of the columns, in this case you need to alter constants on your model class.
Your model is now extended from Node class, not Eloquent:
class Foo extends Node {
}If you're using custom columns, you need to make shure that it's reflected on the model:
class Foo extends Node {
const LFT = 'lft';
const RGT = 'rgt';
const PARENT_ID = 'parent';
protected $guarded = [ 'lft', 'rgt' ];
// To allow mass asignment on parent attribute
public function setParentAttribute($value)
{
$this->setParentIdAttribute($value);
}
}Important! Make sure that lft and rgt columns are guarded!
Copyright (c) 2014 Alexander Kalnoy
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