Custom Packages and Asset Workflow

Unity's Package Manager allows you to create reusable toolkits distributed as packages. Custom packages can be shared via local paths, git repositories, or the Unity Asset Store.

Package Structure

A valid Unity package requires a specific folder layout:

com.yourname.mypackage/
  package.json         <- Required manifest file
  Runtime/             <- C

### scripts used at runtime

### MyPackage.asmdef   <- Assembly Definition

### Editor/              <- Editor-only scripts

### MyPackageEditor.asmdef

### Tests/               <- Unit tests
  Documentation~/      <- Markdown documentation (not imported)

### README.md

### CHANGELOG.md

### LICENSE.md

The package.json Manifest

json
{
  "name": "com.yourname.mypackage",
  "version": "1.0.0",
  "displayName": "My Awesome Package",
  "description": "A reusable toolkit for Unity projects.",
  "unity": "6000.0",
  "unityRelease": "0f1",
  "author": {
    "name": "Your Name",
    "email": "you@example.com"
  },
  "dependencies": {
    "com.unity.inputsystem": "1.7.0"
  }
}

Installing a Local Package

In the Package Manager, click the + button and choose:

• Add package from disk: Browse to the folder containing package.json.
• Add package from git URL: Enter a git repository URL.

json
// In your project's Packages/manifest.json
{
  "dependencies": {
    "com.yourname.mypackage": "file:../path/to/com.yourname.mypackage",
    "com.yourname.gitpackage": "https://github.com/you/repo.git#v1.0.0"
  }
}

Assembly Definitions for Packages

Each folder inside your package should have an Assembly Definition (.asmdef) file to:

• Create a separate compiled assembly (speeds up compilation).
• Define access control (which assemblies can reference yours).
• Separate Editor and Runtime code.

json
// Runtime/MyPackage.asmdef
{
  "name": "YourName.MyPackage",
  "rootNamespace": "YourName.MyPackage",
  "references": [],
  "includePlatforms": [],
  "excludePlatforms": [],
  "autoReferenced": true
}

AssetDatabase Scripting

When writing Editor tools, use AssetDatabase to manage assets programmatically:

csharp
using UnityEditor;
using UnityEngine;

public class AssetTool
{
    [MenuItem("Tools/Create Default Material")]
    static void CreateMaterial()
    {
        Material mat = new Material(Shader.Find("Universal Render Pipeline/Lit"));
        AssetDatabase.CreateAsset(mat, "Assets/DefaultMaterial.mat");

### AssetDatabase.SaveAssets();

### AssetDatabase.Refresh();

### EditorUtility.FocusProjectWindow();

### Selection.activeObject = mat;
    }
}

TL;DR

• Custom packages require a package.json manifest and a specific folder structure.
• Name packages with reverse domain notation: com.company.packagename.
• Use Assembly Definitions to isolate Runtime vs Editor code and speed up compilation.
• Reference local packages via file paths or git URLs in the project's manifest.json.