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

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

static NSString* _storageDirectoryPath();
+ (NSString *)_storageDirectoryPath;

#include "WebStorageManagerPrivate.h"

#include "WebPreferencesPrivate.h"

NSString* dbPath = [WebStorageManager _storageDirectoryPath];

    WebPreferences* prefs = [self.webView preferences];
    NSString* localDBPath = [prefs _localStorageDatabasePath];

        // PATHS MUST MATCH!!!!  otherwise localstorage file is erased when starting program
    if( [localDBPath isEqualToString:dbPath] == NO) {
        [prefs setAutosaves:YES];  //SET PREFS AUTOSAVE FIRST otherwise settings aren't saved.
        // Define application cache quota
        static const unsigned long long defaultTotalQuota = 10 * 1024 * 1024; // 10MB
        static const unsigned long long defaultOriginQuota = 5 * 1024 * 1024; // 5MB
        [prefs setApplicationCacheTotalQuota:defaultTotalQuota];
        [prefs setApplicationCacheDefaultOriginQuota:defaultOriginQuota];

        [prefs setWebGLEnabled:YES];
        [prefs setOfflineWebApplicationCacheEnabled:YES];

        [prefs setDatabasesEnabled:YES];
        [prefs setDeveloperExtrasEnabled:[[NSUserDefaults standardUserDefaults] boolForKey: @"developer"]];
#ifdef DEBUG
        [prefs setDeveloperExtrasEnabled:YES];
#endif
        [prefs _setLocalStorageDatabasePath:dbPath];
        [prefs setLocalStorageEnabled:YES];

        [self.webView setPreferences:prefs];
    }