How do I enable Local Storage in my WebKit-based application?

Question

I have a Cocoa/Objective-C application which embeds a WebKit WebView. I need to turn on database support and local storage. I know it can be done--I have it working in Safari--but I can't find an example of how to set this up in my own application.

I found this (unanswered) SO question which provides an example but, as the original poster mentions, doesn't work. And in fact, the methods he uses (setDatabasesEnabled, setLocalStorageEnabled) aren't defined in my WebKit.framework (Xcode 3.2.5), although they appear to exist if I define them myself.

Can anyone provide an example of how to enable local database storage for a WebKit-based Cocoa application? Many thanks if so!

Update: I've got something working...I was confused by "databases" vs. "local storage", which are apparently quite different things. Here's the code that works:

WebPreferences* prefs = [webView preferences];
[prefs _setLocalStorageDatabasePath:@"~/Library/Application Support/MyApp"];
[prefs setLocalStorageEnabled:YES];

So that works, but it requires the private method _setLocalStorageDatabasePath, which means no App Store for me. So my amended questions is now: is there a way to make this work without using a private method? I found the WebDatabaseDirectory preference key in this answer, which controls where databases go. But I couldn't find a corresponding key for local storage anywhere in the sources. Or is there a way for me to force local storage to use the database, and so the WebDatabaseDirectory key? Any ideas?

Answer 1

I submitted an app using this code to the Mac App Store, and Apple approved it:

Objective-C

WebPreferences* prefs = [webView preferences];
[prefs _setLocalStorageDatabasePath:@"~/Library/Application Support/MyApp"];
[prefs setLocalStorageEnabled:YES];

Swift 3

var prefs: WebPreferences? = webView.preferences
prefs?._setLocalStorageDatabasePath("~/Library/Application Support/MyApp")
prefs?.localStorageEnabled = true

Whether they will continue to approve that, I don't know, but they allowed it for my application as of 2011-01-29. Update: They also approved a version update to the same app, so it has gone through twice.