Nested Set for Go

Nested Set is an implementation of the Nested set model for Gorm.

This project is the Go version of awesome_nested_set, which uses the same data structure design, so it uses the same data together with awesome_nested_set.

Actually the original design is for this, the content managed by awesome_nested_set in our Rails application, the front-end Go API also needs to be maintained.

This is a Go version of the awesome_nested_set, and it built for compatible with awesome_nested_set.

Usage

Define the model

You must use nestedset Stuct tag to define your Gorm model like this:

Support struct tags:

• id - int64 - Primary key of the node
• parent_id - sql.NullInt64 - ParentID column, null is root
• lft - int
• rgt - int
• depth - int - Depth of the node
• children_count - Number of children

Optional:

• scope - restricts what is to be considered a list. You can also setup scope by multiple attributes.

Example:

import (
	"database/sql"
	"github.com/fox-gonic/fox/database/nestedset"
)

// Category
type Category struct {
	ID            int64         `gorm:"PRIMARY_KEY;AUTO_INCREMENT" nestedset:"id"`
	ParentID      sql.NullInt64 `nestedset:"parent_id"`
	UserType      string        `nestedset:"scope"`
	UserID        int64         `nestedset:"scope"`
	Rgt           int           `nestedset:"rgt"`
	Lft           int           `nestedset:"lft"`
	Depth         int           `nestedset:"depth"`
	ChildrenCount int           `nestedset:"children_count"`
	Title         string
}

Move Node

import nestedset "github.com/fox-gonic/fox/database/nestedset"

// create a new node root level last child
nestedset.Create(tx, &node, nil)

// create a new node as parent first child
nestedset.Create(tx, &node, &parent)

// nestedset.MoveDirectionLeft
// nestedset.MoveDirectionRight
// nestedset.MoveDirectionInner
nestedset.MoveTo(tx, node, to, nestedset.MoveDirectionLeft)

Get Nodes with tree order

// With scope, limit tree in a scope
tx := db.Model(&Category{}).Where("user_type = ? AND user_id = ?", "User", 100)

// Get all nodes
categories, _ := tx.Order("lft asc").Error

// Get root nodes
categories, _ := tx.Where("parent_id IS NULL").Order("lft asc").Error

// Get childrens
categories, _ := tx.Where("parent_id = ?", parentCategory.ID).Order("lft asc").Error

Testing

$ createdb nested-set-test
$ go test ./...

-- some useful sql to check status
SELECT n.id,
CONCAT(REPEAT('. . ', (COUNT(p.id) - 1)::int), n.title) AS t,
n.title, n.lft, n.rgt, n.depth, n.children_count
FROM categories AS n, categories AS p
WHERE (n.lft BETWEEN p.lft AND p.rgt)
GROUP BY n.id ORDER BY n.lft;

License

MIT