ICloud 基础知识和代码示例

对待 iCloud 中的文件就像对待应用程序沙盒中的所有其他文件一样。

然而，在我的情况下，没有“正常”的应用程序沙箱了。在云端。或者我总是先从磁盘加载 text.txt，然后再用 iCloud 检查是否有更新的内容？

相关问题: 文件结构-沙盒与云

也许我的主要问题是对 iCloud 应该如何工作的根本性误解。当我创建一个 UIDdocument 的新实例时，我必须重写两个方法。首先 - (BOOL)loadFromContents:(id)contents ofType:(NSString *)typeName error:(NSError **)outError从云中获取文件，然后 -(id)contentsForType:(NSString *)typeName error:(NSError **)outError从云中获取文件。

我是否需要合并一些单独的函数，这些函数也会将 text.txt 的本地副本保存到我的沙箱中？这对非 iCloud 用户有用吗？据我所知，iCloud 会自动保存 text.txt 的本地副本。因此，我不需要将任何东西保存到我的应用程序的“旧”沙箱中(也就是说，在 iCloud 诞生之前，它曾经是旧的)。现在，我的沙盒是完全空的，但我不知道这是否正确。我是不是应该在里面再放一份 text.txt？这感觉就像我的数据结构混乱... 因为有一个 text.txt 在云中，一个在我的设备上的 iCloud 沙盒中(即使我离线也能工作) ，第三个在我的应用程序的沙盒中..。

我的代码: 一个简单的 iCloud 示例代码

这是松散的基于一个例子，我发现在开发人员论坛和 WWDC 会话视频。我把它削减到最低限度。我不确定我的 MVC 结构是否好。这个模型位于不理想的应用委托中。任何改进的建议都是受欢迎的。

编辑: 我试图摘录主要问题并发表在这里

概述:

从云中加载 text.txt 的最重要的部分是:

//  AppDelegate.h
//  iCloudText


#import <UIKit/UIKit.h>


@class ViewController;
@class MyTextDocument;


@interface AppDelegate : UIResponder <UIApplicationDelegate> {
NSMetadataQuery *_query;
}


@property (strong, nonatomic) UIWindow *window;
@property (strong, nonatomic) ViewController *viewController;
@property (strong, nonatomic) MyTextDocument *document;


@end


//  AppDelegate.m
//  iCloudText


#import "AppDelegate.h"
#import "MyTextDocument.h"
#import "ViewController.h"


@implementation AppDelegate


@synthesize window = _window;
@synthesize viewController = _viewController;
@synthesize document = _document;


- (void)dealloc
{
[_window release];
[_viewController release];
[super dealloc];
}


- (void)loadData:(NSMetadataQuery *)query {


// (4) iCloud: the heart of the load mechanism: if texts was found, open it and put it into _document; if not create it an then put it into _document


if ([query resultCount] == 1) {
// found the file in iCloud
NSMetadataItem *item = [query resultAtIndex:0];
NSURL *url = [item valueForAttribute:NSMetadataItemURLKey];


MyTextDocument *doc = [[MyTextDocument alloc] initWithFileURL:url];
//_document = doc;
doc.delegate = self.viewController;
self.viewController.document = doc;


[doc openWithCompletionHandler:^(BOOL success) {
if (success) {
NSLog(@"AppDelegate: existing document opened from iCloud");
} else {
NSLog(@"AppDelegate: existing document failed to open from iCloud");
}
}];
} else {
// Nothing in iCloud: create a container for file and give it URL
NSLog(@"AppDelegate: ocument not found in iCloud.");


NSURL *ubiq = [[NSFileManager defaultManager] URLForUbiquityContainerIdentifier:nil];
NSURL *ubiquitousPackage = [[ubiq URLByAppendingPathComponent:@"Documents"] URLByAppendingPathComponent:@"text.txt"];


MyTextDocument *doc = [[MyTextDocument alloc] initWithFileURL:ubiquitousPackage];
//_document = doc;
doc.delegate = self.viewController;
self.viewController.document = doc;


[doc saveToURL:[doc fileURL] forSaveOperation:UIDocumentSaveForCreating completionHandler:^(BOOL success) {
NSLog(@"AppDelegate: new document save to iCloud");
[doc openWithCompletionHandler:^(BOOL success) {
NSLog(@"AppDelegate: new document opened from iCloud");
}];
}];
}
}


- (void)queryDidFinishGathering:(NSNotification *)notification {


// (3) if Query is finished, this will send the result (i.e. either it found our text.dat or it didn't) to the next function


NSMetadataQuery *query = [notification object];
[query disableUpdates];
[query stopQuery];


[self loadData:query];


[[NSNotificationCenter defaultCenter] removeObserver:self name:NSMetadataQueryDidFinishGatheringNotification object:query];
_query = nil; // we're done with it
}


-(void)loadDocument {


// (2) iCloud query: Looks if there exists a file called text.txt in the cloud


NSMetadataQuery *query = [[NSMetadataQuery alloc] init];
_query = query;
//SCOPE
[query setSearchScopes:[NSArray arrayWithObject:NSMetadataQueryUbiquitousDocumentsScope]];
//PREDICATE
NSPredicate *pred = [NSPredicate predicateWithFormat: @"%K == %@", NSMetadataItemFSNameKey, @"text.txt"];
[query setPredicate:pred];
//FINISHED?
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(queryDidFinishGathering:) name:NSMetadataQueryDidFinishGatheringNotification object:query];
[query startQuery];


}


- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
NSLog(@"AppDelegate: app did finish launching");
self.window = [[[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]] autorelease];


// Override point for customization after application launch.
if ([[UIDevice currentDevice] userInterfaceIdiom] == UIUserInterfaceIdiomPhone) {
self.viewController = [[[ViewController alloc] initWithNibName:@"ViewController_iPhone" bundle:nil] autorelease];
} else {
self.viewController = [[[ViewController alloc] initWithNibName:@"ViewController_iPad" bundle:nil] autorelease];
}


self.window.rootViewController = self.viewController;
[self.window makeKeyAndVisible];


// (1) iCloud: init


NSURL *ubiq = [[NSFileManager defaultManager] URLForUbiquityContainerIdentifier:nil];
if (ubiq) {
NSLog(@"AppDelegate: iCloud access!");
[self loadDocument];
} else {
NSLog(@"AppDelegate: No iCloud access (either you are using simulator or, if you are on your phone, you should check settings");
}




return YES;
}


@end

UID 文件

//  MyTextDocument.h
//  iCloudText


#import <Foundation/Foundation.h>
#import "ViewController.h"


@interface MyTextDocument : UIDocument {


NSString *documentText;
id delegate;


}


@property (nonatomic, retain) NSString *documentText;
@property (nonatomic, assign) id delegate;


@end


//  MyTextDocument.m
//  iCloudText


#import "MyTextDocument.h"
#import "ViewController.h"


@implementation MyTextDocument


@synthesize documentText = _text;
@synthesize delegate = _delegate;


// ** READING **


- (BOOL)loadFromContents:(id)contents ofType:(NSString *)typeName error:(NSError **)outError
{
NSLog(@"UIDocument: loadFromContents: state = %d, typeName=%@", self.documentState, typeName);


if ([contents length] > 0) {
self.documentText = [[NSString alloc] initWithBytes:[contents bytes] length:[contents length] encoding:NSUTF8StringEncoding];
}
else {
self.documentText = @"";
}


NSLog(@"UIDocument: Loaded the following text from the cloud: %@", self.documentText);




// update textView in delegate...
if ([_delegate respondsToSelector:@selector(noteDocumentContentsUpdated:)]) {
[_delegate noteDocumentContentsUpdated:self];
}


return YES;


}


// ** WRITING **


-(id)contentsForType:(NSString *)typeName error:(NSError **)outError
{
if ([self.documentText length] == 0) {
self.documentText = @"New Note";
}


NSLog(@"UIDocument: Will save the following text in the cloud: %@", self.documentText);


return [NSData dataWithBytes:[self.documentText UTF8String] length:[self.documentText length]];
}
@end

观察控制器

//
//  ViewController.h
//  iCloudText


#import <UIKit/UIKit.h>


@class MyTextDocument;


@interface ViewController : UIViewController <UITextViewDelegate> {


IBOutlet UITextView *textView;


}


@property (nonatomic, retain) UITextView *textView;
@property (strong, nonatomic) MyTextDocument *document;


-(void)noteDocumentContentsUpdated:(MyTextDocument *)noteDocument;


@end


//  ViewController.m
//  iCloudText


#import "ViewController.h"
#import "MyTextDocument.h"


@implementation ViewController


@synthesize textView = _textView;
@synthesize document = _document;


-(IBAction)dismissKeyboard:(id)sender {


[_textView resignFirstResponder];


}


-(void)noteDocumentContentsUpdated:(MyTextDocument *)noteDocument
{
NSLog(@"VC: noteDocumentsUpdated");
_textView.text = noteDocument.documentText;
}


-(void)textViewDidChange:(UITextView *)theTextView {


NSLog(@"VC: textViewDidChange");
_document.documentText = theTextView.text;
[_document updateChangeCount:UIDocumentChangeDone];


}