UGTK / Toolkit / Utility Systems / Folder Path System Completed

Folder Path System

Summary

The Folder Path System solves "let the user pick a folder" twice over: a [FolderPath] attribute that turns any string field into a text box with a … browse button in the inspector, and an Mn_FolderPicker component that opens a real folder dialog at runtime — the native Windows browser in a standalone build, Unity's own panel in the editor — reporting the result through UnityEvents.

It is the piece you need for a kiosk that exports photos, a tool that writes a report, or any build that has to ask the operator where to save.

Modules Dependencies

None. No UGTK reference. The runtime picker uses a P/Invoke into the Windows shell (SHBrowseForFolder), which is bundled with the module.

Setup

There is no GIF for this module: every meaningful action opens an operating-system folder dialog, which is outside Unity and would put the machine's folder tree in the documentation.

In the inspector: decorate a string field with [FolderPath].
At runtime: drop the SelectFolderButton prefab under a Canvas — a Button already wired to Mn_FolderPicker.PickFolder() — or add Mn_FolderPicker to a GameObject and bind the button yourself.

How To Use

The attribute

using UGTK.UtilitySystems.FolderPathSystem;

public class Exporter : MonoBehaviour
{
    [FolderPath] public string outputFolder;
}

The drawer renders a normal text field plus a … button that opens EditorUtility.OpenFolderPanel starting from Application.dataPath, and writes back the absolute path. On a field that is not a string it draws a warning instead of the field — no silent failure.

The runtime component

Folder Path: the current path, itself decorated with [FolderPath], so you can also set it by hand from the inspector.
Dialog Title: the caption of the dialog.
Create If Missing (default on): if the chosen folder no longer exists it is created.
Events: onFolderPicked(string), onCancelled, onError(string) in the inspector, plus the C# events FolderPicked, Cancelled, Error for code that wires itself.

folderPicker.PickFolder();          // 0 params: bind it straight to Button.onClick
folderPicker.SetFolder(path);       // set from code (same validation and events)
folderPicker.ClearFolder();         // empties it
string current = folderPicker.FolderPath;   // read-only property

Good to know:

Platforms. In the editor (edit mode) it uses Unity's panel; in a Windows standalone build it opens the native shell browser. On any other runtime platform — macOS, Linux, Android, WebGL — it does not silently fail: it raises onError. Handle that event, or the button will look broken.
Absolute paths, not asset paths. What you get back is a filesystem path (C:\Users\…\Documents\Export), not Assets/…: fine for System.IO, not usable with AssetDatabase.
Cancelling is not an error: closing the dialog fires onCancelled and leaves the previous path untouched.
A path saved in the editor will not exist on another machine: treat the inspector value as a default, and let the operator pick at runtime.

Testing Scene

Open Debug/FolderPathScene.unity. It holds FolderPicker with Mn_FolderPicker — the component itself — and FolderPath Example, which shows the same value being consumed. Everything worth pressing is in the inspector's Editor Test Tools.

Current folder shows the stored path and, under it, the answer that actually matters: whether the folder exists and is writable. A folder that exists but is read-only fails at save time, far away from the choice that caused it, so the check is here rather than there.
Type a path into Path and press SetFolder(). With Create If Missing on, a folder that is not there yet is created, and the message flips to exists and is writable.
Use persistentDataPath fills in Unity's own writable folder — the safe default on every platform.
ClearFolder() forgets it.

PickFolder() opens the real Windows dialog and is the one control this scene cannot script: it blocks the editor until you answer it. It is also Windows-only — on other platforms the component says so and SetFolder is the way in.

One asymmetry worth knowing: SetFolder normalises the path and honours Create If Missing, exactly as a pick does, but it deliberately does not raise onFolderPicked. Restoring a saved preference at startup is not the user choosing a folder, and a listener that uploads or saves on that event would fire on every launch.

Technical Info

Path	Content
`Scripts/Attribute/FolderPathAttribute.cs`	Marker `PropertyAttribute`
`Scripts/Attribute/FolderPathDrawer.cs`	`PropertyDrawer`: text field + … button, with the string-type guard
`Scripts/Mn_FolderPicker.cs`	Runtime component: editor/native dialog, validation, folder creation, UnityEvents and C# events. Contains the `WindowsNativeFolderPicker` P/Invoke wrapper
`Prefabs/SelectFolderButton.prefab`	Button already wired to `PickFolder()`
`Debug/Mn_FolderPathExample.cs`	Minimal example of the attribute
`Debug/FolderPathScene.unity`	Test scene

Mn_FolderPicker API: PickFolder(), SetFolder(string), ClearFolder(), FolderPath, events onFolderPicked / onCancelled / onError and FolderPicked / Cancelled / Error.