Tree

The tree package provides a generic tree builder that converts flat slices into hierarchical tree structures.

Quick Start

import "github.com/coldsmirk/vef-framework-go/tree"

type Department struct {
    ID       string        `json:"id"`
    ParentID *string       `json:"parentId"`
    Name     string        `json:"name"`
    Children []Department  `json:"children"`
}

// Define the adapter
adapter := tree.Adapter[Department]{
    GetID:       func(d Department) string { return d.ID },
    GetParentID: func(d Department) *string { return d.ParentID },
    GetChildren: func(d Department) []Department { return d.Children },
    SetChildren: func(d *Department, children []Department) { d.Children = children },
}

// Build tree from flat slice
roots := tree.Build(flatDepartments, adapter)

Adapter

The Adapter[T] struct defines how the tree builder accesses node properties:

type Adapter[T any] struct {
    GetID       func(T) string      // Extract node ID
    GetParentID func(T) *string     // Extract parent ID (nil = root node)
    GetChildren func(T) []T         // Get children slice
    SetChildren func(*T, []T)       // Set children slice
}

Key rules:

• Nodes with nil parent ID are treated as roots
• Nodes whose parent ID references a non-existent node are also treated as roots
• Circular references are protected against via visited tracking

Finding Nodes

FindNode

Search for a node by ID in a tree:

node, found := tree.FindNode(roots, "dept-123", adapter)
if found {
    fmt.Println(node.Name)
}

FindNodePath

Get the full path from root to a target node:

path, found := tree.FindNodePath(roots, "dept-456", adapter)
if found {
    for _, node := range path {
        fmt.Println(node.Name) // prints: "Root" → "Parent" → "dept-456"
    }
}

Framework Integration

The tree package is used by the CRUD FindTree builder. When you create a tree endpoint:

crud.NewFindTree[Department, DepartmentSearch](tree.Build)

The framework passes tree.Build as the tree builder function, using the model's tree adapter configuration.