iCloud基础和代码示例[关闭](iCloud basics and code sample [closed])

 作为初学者，我正在努力与iCloud。 有一些样本，但它们通常是非常详细的（在开发者论坛上有一个用于iCloud和CoreData是巨大的）。 苹果文档可以，但我仍然看不到大图。 所以请跟我一起，其中一些问题是很根本的，但可能很容易回答。 
 
 上下文：我有一个非常简单的iCloud应用程序运行（下面是完整的示例代码）。 只有一个UITextView显示给用户，他/她的输入被保存在一个名为text.txt的文件中。 
 
 
 txt文件被推送到云端并提供给所有设备。 完美的工作，但： 
 
 主要问题：不使用iCloud的用户怎么办？ 
 
 当我启动我的应用程序（见下面的代码），我检查用户是否启用了iCloud。 如果启用了iCloud，一切都很好。 该应用程序继续前进，并在云中查找text.txt。 如果找到，它将加载它并显示给用户。 如果在云中找不到text.txt，则只需创建一个新的text.txt并将其显示给用户。 
 
 如果用户没有启用iCloud，则不会发生任何事情。 如何使非iCloud用户仍然可以使用我的文本应用程序？ 还是我忽略它们？ 我需要为非iCloud用户编写单独的功能吗？ 即，我只是从文件夹中加载一个text.txt的功能？ 
 
 苹果写道 ： 
 
 
 
 在iCloud中处理文件与处理应用程序沙箱中的所有其他文件相同。 
 
 
 但是，在我的情况下，没有“正常”应用程序沙箱了。 它在云端。 或者我总是从磁盘首先加载我的text.txt，然后检查iCloud是否有更新的东西？ 
 
 相关问题：文件结构 - Sandbox vs. Cloud 
 
 也许我的主要问题是对iCloud如何运作的根本误解。 当我创建一个UIDocument的新实例时，我必须覆盖两个方法。 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将文件导入云端。 
 
 我必须包含单独的功能，还将text.txt的本地副本保存到我的沙箱中？ 这将为非iCloud用户工作吗？ 据了解iCloud，它将自动保存本地的text.txt副本。 所以我不应该有任何需要保存任何东西到我的应用程序的“旧”沙箱（即以前是旧的，在iCloud之前）。 现在，我的沙箱完全是空的，但我不知道这是否正确。 我应该保留另一个text.txt的副本吗？ 这感觉像是混乱我的数据结构...因为云中有一个text.txt，一个在我的设备上的iCloud沙箱（即使我离线）也可以工作），另一个在旧的沙箱我的应用程式 
 
 
 我的代码：一个简单的iCloud示例代码 
 
 这是基于我在开发者论坛和WWDC会话视频中发现的一个例子。 我把它剥离到最低限度。 我不确定我的MVC结构是否有好处。 AppDelegate中的模型是不理想的。 欢迎任何建议，使其更好。 
 
 
 编辑：我试图提取主要问题并张贴[这里]。 4 
 
 
 概述： 
 
 
 从云中加载text.txt的最重要的一点： 
 
//  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
 
 
 UIDocument 
 
//  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
 
 
 VIEWCONTROLLER 
 
//
//  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];

}

As a beginner, I'm struggling with iCloud. There are some samples, but they are usually quite detailed (on the developer forum there is one for iCloud and CoreData which is massive). The apple docs are OK, but I still can't see the big picture. So please bear with me, some of these questions are quite fundamental, but possibly easy to answer.
 
Context: I have a very simple iCloud app running (full sample code below). There is only one UITextView shown to the user and his/her input is saved in a file called text.txt.
 
 
The txt file is pushed to the cloud and made available to all devices. Works perfectly, but:
 
Main problem: What about users who do not use iCloud?
 
When I launch my app (see code below), I check if the user has iCloud enabled. If iCloud is enabled, everything is fine. The app goes ahead and looks for text.txt in the cloud. If found, it will load it and display it to the user. If text.txt is not found in the cloud, it will simply create a new text.txt and will display that to the user. 
 
If the user does not have iCloud enabled, nothing will happen. How will I make it possible that non-iCloud users can still work with my text app? Or do I simply ignore them? Would I need to write separate functions for non-iCloud users? I.e. functions in which I simply load a text.txt from the documents folder?
 
Apple writes: 
 
 
 
Treat files in iCloud the same way you treat all other files in your app sandbox.
 
 
However, in my case there is no 'normal' app sandbox anymore. It's in the cloud. Or do I always load my text.txt from disk first and then check with iCloud if there is something more up-to-date?
 
Related problem: File structure - Sandbox vs. Cloud
 
Perhaps my main problem is a fundamental misunderstanding of how iCloud is supposed to work. When I create a new instance of an UIDocument, I'll have to overwrite two methods. First - (BOOL)loadFromContents:(id)contents ofType:(NSString *)typeName error:(NSError **)outError to get files from the cloud and then -(id)contentsForType:(NSString *)typeName error:(NSError **)outError to get files into the cloud.
 
Do I have to incorporate separate functions which will also save a local copy of text.txt into my sandbox? Will this work for non-iCloud users? As I understand iCloud, it will save a local copy of text.txt automatically. So there shouldn't be any need for me save anything into the 'old' sandbox of my app (i.e. as it used to be in the old, pre-iCloud days). Right now, my sandbox is totally empty, but I don't know if this is correct. Should I keep another copy of text.txt in there? This feels like cluttering my data structure... as there is one text.txt in the cloud, one in the iCloud sandbox on my device (which will work even if I am offline), and a third one in the good old sandbox of my app...
 
 
MY CODE: A simple iCloud sample code
 
This is loosely based on an example I found in the developer forum and on the WWDC session video. I stripped it down to the bare minimum. I'm not sure that my MVC structure is any good. The model is in the AppDelegate which isn't ideal. Any suggestions to make it better are welcome.
 
 
EDIT: I tried to extract the main question and posted it [here].4
 
 
OVERVIEW:
 
 
The most important bit which loads the text.txt from the cloud:
 
//  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
 
 
The UIDocument
 
//  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
 
 
THE VIEWCONTROLLER
 
//
//  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];

}

原文：https://stackoverflow.com/questions/7795629