什么是文档目录(NSDocumentDirectory)？

Question

有人能给我解释一下iOS应用上的文档目录是什么吗?什么时候使用它？

以下是我目前所相信的：

对我来说，它似乎是一个中央文件夹，用户可以在其中存储应用程序所需的任何文件。

这是否与Core data存储数据的位置不同？

似乎每个应用程序都有自己的文档目录。

我可以自由地创建文档目录的子目录，如文档目录/image或文档目录/videos？

Answer 1

您的应用程序只能(在未越狱的设备上)在“沙箱”环境中运行。这意味着它只能访问自己内容中的文件和目录。例如，文档和库。

请参阅。

要访问应用程序沙箱的Documents目录，可以使用以下命令：

iOS 8和更高版本，这是推荐的方法

+ (NSURL *)applicationDocumentsDirectory
{
     return [[[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask] lastObject];
}

如果您需要支持iOS 7或更早版本

+ (NSString *) applicationDocumentsDirectory 
{    
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *basePath = paths.firstObject;
    return basePath;
}

此Documents目录允许您存储应用程序创建或可能需要的文件和子目录。

要访问应用程序沙箱的库目录中的文件，请使用(代替上面的paths )：

[NSSearchPathForDirectoriesInDomains(NSLibraryDirectory, NSUserDomainMask, YES) objectAtIndex:0]

Answer 2

这在iOS 8中发生了变化。请参阅以下技术说明：https://developer.apple.com/library/ios/technotes/tn2406/_index.html

Apple认可的方式(来自上面的链接)如下所示：

// Returns the URL to the application's Documents directory.
- (NSURL *)applicationDocumentsDirectory
{
    return [[[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask] lastObject];
}

Answer 3

我在文档中找不到被接受的答案建议的代码，但我在这里找到了更新后的等价物：

- (NSURL*)applicationDataDirectory {
    NSFileManager* sharedFM = [NSFileManager defaultManager];
    NSArray* possibleURLs = [sharedFM URLsForDirectory:NSApplicationSupportDirectory
                                 inDomains:NSUserDomainMask];
    NSURL* appSupportDir = nil;
    NSURL* appDirectory = nil;

    if ([possibleURLs count] >= 1) {
        // Use the first directory (if multiple are returned)
        appSupportDir = [possibleURLs objectAtIndex:0];
    }

    // If a valid app support directory exists, add the
    // app's bundle ID to it to specify the final directory.
    if (appSupportDir) {
        NSString* appBundleID = [[NSBundle mainBundle] bundleIdentifier];
        appDirectory = [appSupportDir URLByAppendingPathComponent:appBundleID];
    }

    return appDirectory;
}

它不鼓励使用NSSearchPathForDirectoriesInDomain：

NSSearchPathForDirectoriesInDomains函数的行为类似于URLsForDirectory，但它将目录的位置作为基于字符串的路径返回。您应该改用URLsForDirectory:inDomains:方法。

下面是其他一些有用的目录常量。毫无疑问，并不是所有这些都在iOS中得到支持。您还可以使用NSHomeDirectory()函数，该函数：

在iOS中，主目录是应用程序的沙箱目录。在OS X中，它是应用程序的沙箱目录或当前用户的主目录(如果应用程序不在沙箱中)

来自NSPathUtities.h的

NSApplicationDirectory = 1,             // supported applications (Applications)
    NSDemoApplicationDirectory,             // unsupported applications, demonstration versions (Demos)
    NSDeveloperApplicationDirectory,        // developer applications (Developer/Applications). DEPRECATED - there is no one single Developer directory.
    NSAdminApplicationDirectory,            // system and network administration applications (Administration)
    NSLibraryDirectory,                     // various documentation, support, and configuration files, resources (Library)
    NSDeveloperDirectory,                   // developer resources (Developer) DEPRECATED - there is no one single Developer directory.
    NSUserDirectory,                        // user home directories (Users)
    NSDocumentationDirectory,               // documentation (Documentation)
    NSDocumentDirectory,                    // documents (Documents)
    NSCoreServiceDirectory,                 // location of CoreServices directory (System/Library/CoreServices)
    NSAutosavedInformationDirectory NS_ENUM_AVAILABLE(10_6, 4_0) = 11,   // location of autosaved documents (Documents/Autosaved)
    NSDesktopDirectory = 12,                // location of user's desktop
    NSCachesDirectory = 13,                 // location of discardable cache files (Library/Caches)
    NSApplicationSupportDirectory = 14,     // location of application support files (plug-ins, etc) (Library/Application Support)
    NSDownloadsDirectory NS_ENUM_AVAILABLE(10_5, 2_0) = 15,              // location of the user's "Downloads" directory
    NSInputMethodsDirectory NS_ENUM_AVAILABLE(10_6, 4_0) = 16,           // input methods (Library/Input Methods)
    NSMoviesDirectory NS_ENUM_AVAILABLE(10_6, 4_0) = 17,                 // location of user's Movies directory (~/Movies)
    NSMusicDirectory NS_ENUM_AVAILABLE(10_6, 4_0) = 18,                  // location of user's Music directory (~/Music)
    NSPicturesDirectory NS_ENUM_AVAILABLE(10_6, 4_0) = 19,               // location of user's Pictures directory (~/Pictures)
    NSPrinterDescriptionDirectory NS_ENUM_AVAILABLE(10_6, 4_0) = 20,     // location of system's PPDs directory (Library/Printers/PPDs)
    NSSharedPublicDirectory NS_ENUM_AVAILABLE(10_6, 4_0) = 21,           // location of user's Public sharing directory (~/Public)
    NSPreferencePanesDirectory NS_ENUM_AVAILABLE(10_6, 4_0) = 22,        // location of the PreferencePanes directory for use with System Preferences (Library/PreferencePanes)
    NSApplicationScriptsDirectory NS_ENUM_AVAILABLE(10_8, NA) = 23,      // location of the user scripts folder for the calling application (~/Library/Application Scripts/code-signing-id)
    NSItemReplacementDirectory NS_ENUM_AVAILABLE(10_6, 4_0) = 99,       // For use with NSFileManager's URLForDirectory:inDomain:appropriateForURL:create:error:
    NSAllApplicationsDirectory = 100,       // all directories where applications can occur
    NSAllLibrariesDirectory = 101,          // all directories where resources can occur
    NSTrashDirectory NS_ENUM_AVAILABLE(10_8, NA) = 102                   // location of Trash directory

最后，介绍了NSURL类别http://club15cc.com/code/ios/easy-ios-file-directory-paths-with-this-handy-nsurl-category中的一些方便方法