我正在尝试使用Core Data制作iPhone应用程序。我必须使用NSManagedObjectContext来访问数据，为了做到这一点，我使用了UIManagedDocument。但是，如果我尝试使用UIManagedDocument创建文档，则文档的openWithCompletionHandler不会成功。这就是为什么我的NSManagedObjectContext总是nil而Xcode说不能在等等处创建文档。以下是类：
AddUserViewController.h
#import <UIKit/UIKit.h>
@interface AddUserViewController : UIViewController
@property (nonatomic, strong) NSManagedObjectContext *managedObjectContext;
@property (nonatomic,strong) UIManagedDocument *document;
@end
AddUserViewController.m
#import "AddUserViewController.h"
#import "User.h"
#import "User+Create.h"
@interface AddUserViewController ()
@property (weak, nonatomic) IBOutlet UITextField *nameField;
@property (weak, nonatomic) IBOutlet UITextField *ageField;
@property (weak, nonatomic) IBOutlet UITextField *sexField;
@property (weak, nonatomic) IBOutlet UITextField *weightField;
@property (weak, nonatomic) IBOutlet UITextField *activityField;
@end
@implementation AddUserViewController
-(void)setManagedObjectContext:(NSManagedObjectContext *)managedObjectContext{
_managedObjectContext = managedObjectContext;
}
-(void)createOrWriteDocument{
NSURL *url = [[[NSFileManager defaultManager]URLsForDirectory:NSDocumentationDirectory inDomains:NSUserDomainMask]firstObject];
url = [url URLByAppendingPathComponent:@"Activities"]; // edited mistakenly deleted
self.document = [[UIManagedDocument alloc] initWithFileURL:url];
if ([[NSFileManager defaultManager] fileExistsAtPath:[url path]]) {
[self.document openWithCompletionHandler:^(BOOL success) {
if (success) [self documentIsReady];
if (!success){
NSLog(@"could not open document at %@",url);
}
}];
} else {
[self.document saveToURL:url
forSaveOperation:UIDocumentSaveForCreating
completionHandler:^(BOOL success) {
if (success) {
[self documentIsReady];
}
if (!success){
NSLog(@"could not create document at %@",url);
}
}];
}
}
- (void)documentIsReady
{
if (self.document.documentState == UIDocumentStateNormal) {
self.managedObjectContext = self.document.managedObjectContext;
} }
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view.
if (!self.managedObjectContext) {
[self createOrWriteDocument];
}
UITapGestureRecognizer *tap = [[UITapGestureRecognizer alloc]
initWithTarget:self
action:@selector(dismissKeyboard)];
[self.view addGestureRecognizer:tap];
}
-(void)dismissKeyboard{
[self.nameField resignFirstResponder];
[self.ageField resignFirstResponder];
[self.sexField resignFirstResponder];
[self.weightField resignFirstResponder];
[self.activityField resignFirstResponder];
}
-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender{
if ([segue.identifier isEqualToString:@"setUser:"]) {
//User *user = [[User alloc]init];
User *user = [User createUserWithname:self.nameField.text
withAge:[NSNumber numberWithDouble:[self.ageField.text doubleValue]]
withSex:self.sexField.text
withWeight:[NSNumber numberWithDouble:[self.weightField.text doubleValue]]
withActivity:self.activityField.text
inManagedObjectContext:self.managedObjectContext];
if ([segue.destinationViewController respondsToSelector:@selector(setUser:)]) {
[segue.destinationViewController performSelector:@selector(setUser:) withObject:user];
}
}
}
@end
修改
我解决了问题。问题出在NSURL *url = [[[NSFileManager defaultManager]URLsForDirectory:NSDocumentationDirectory inDomains:NSUserDomainMask]firstObject];
线。我使用NSDocumentDirectory而不是NSDocumentationDirectory，它解决了这个问题。
答案 0 :(得分：0)
您可以尝试使用此代码创建managedobjectcontext。
- (NSManagedObjectContext *) managedObjectContext
{
if (_managedObjectContext != nil) {
return _managedObjectContext;
}
NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator];
if (coordinator != nil) {
_managedObjectContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSMainQueueConcurrencyType];
[_managedObjectContext setPersistentStoreCoordinator: coordinator];
}
return _managedObjectContext;
}
答案 1 :(得分：0)
看一下下面的例子。这对我有用，抱歉没有时间仔细查看差异，我正在使用iCloud选项，所以删除它们但尝试设置其他persistentStoreOptions。还有你错误的错误发布细节吗？
// This gets called when the user has done one of the following:
// 1. Created a new file and entered a new file name. We have then created the fileURL
// using the /Documents directory, the filename and appending '_UUID_'+uuid to ensure that
// avoid duplicate file names in case the user used the same file name on another device.
// 2. Selected an existing file from the file browser
//
- (void)createNewFile:(NSURL*)fileURL {
//FLOG(@"createNewFile called with url %@", fileURL);
_creatingNewFile = YES; // Ignore any file metadata scan events coming in while we do this because some iCloud
// files get created by Core Data before the local files are created and our scanning
// picks up new iCloud files and attempts to create local copies and we don't want this
// if this devices is busy creating the new iCloud file
_document = [[OSManagedDocument alloc] initWithFileURL:fileURL];
// Set oberving on this file to monitor the state (we don't use it for anything other than debugging)
NSNotificationCenter *center = [NSNotificationCenter defaultCenter];
[center addObserver:self
selector:@selector(documentStateChanged:)
name:UIDocumentStateChangedNotification
object:_document];
_openedVersion = [NSFileVersion currentVersionOfItemAtURL:fileURL];
_openedVersionDate = _openedVersion.modificationDate;
_openedVersionDevice = _openedVersion.localizedNameOfSavingComputer;
//FLOG(@" file version date: %@", _openedVersionDate);
//FLOG(@" file version device: %@", _openedVersionDevice);
NSString *fileName = [[fileURL URLByDeletingPathExtension] lastPathComponent];
[_document setPersistentStoreOptions:@{NSPersistentStoreUbiquitousContentNameKey:fileName,
NSMigratePersistentStoresAutomaticallyOption:@YES,
NSInferMappingModelAutomaticallyOption:@YES,
NSSQLitePragmasOption:@{ @"journal_mode" : @"DELETE" }}];
_managedObjectContext = _document.managedObjectContext;
if ([[NSFileManager defaultManager] fileExistsAtPath:[fileURL path]]) {
//FLOG(@" file exists so open it: %@",fileURL);
[_document openWithCompletionHandler:^(BOOL success){
if (!success) {
// Handle the error.
LOG(@" error creating file");
} else {
//LOG(@" file opened");
[self fileOpened]; // Now initialise the UI and let the user continue...
}
}];
}
else {
// File does not exist so that means the user has created a new one and we need to
// load some initialisation data into the Core Data store (codes tables, etc.)
//
// At this stage we have a database in memory so we can just use the _document.managedObjectContext
// to add objects prior to attempting to write to disk.
//LOG(@" file DOES NOT exist so add initial data");
[self addInitialData];
// Just checking if anything has been written to disk, nothing should not exist on disk yet.
// Debugging use only
if ([[NSFileManager defaultManager] fileExistsAtPath:[fileURL path]])
LOG(@" file exists but keep going anyway :-(");
else
LOG(@" file still does not exist :-)");
// OK now save a copy to disk using UIManagedDocument
// NOTE: the iCloud files are written before the UIManagedDocument.fileURL, presumably because Core Data does this setup
// in response to the [moc save:]. Make sure we don't pick this up in our iCloud metaData scan and attempt to create
// it as if it were a new iCloud file created by some other device.
//
[_document saveToURL:_document.fileURL forSaveOperation:UIDocumentSaveForCreating completionHandler:^(BOOL success){
if (!success) {
// Handle the error.
LOG(@" error saving file :-(");
}
// We close the file and wait for it to appear in the file browser and then
// let the user select it from the browser to open it and start using it.
// Skip this if you want to open it directly and [self fileopened] but
// bear in mind the fileListController will not be correctly set up when we return to it.
[_document closeWithCompletionHandler:^(BOOL success){
if (!success) {
// Handle the error.
LOG(@" error closing file after creation :-(");
FLOG(@" file URL is %@", [fileURL path]);
} else {
FLOG(@" file closed %@", fileName);
_creatingNewFile = NO; // OK we are done, so let metaData scanning go ahead as normal
// Tell our UITableView file list that we are done and trigger scanning of local and iCloud files
// The fileListController will the add the new file itself and the user will then pick the
// file from this list in order to open it.
// To open the file automatically use the callback in the fileListController
// to select and then open the file so it looks seamless to the user.
[self.fileListController fileHasBeenCreated:fileURL];
// Stop observing now
[center removeObserver:self
name:UIDocumentStateChangedNotification
object:_document];
}
}];
}];
}
}
哦，还要创建一个UIManagedDocument的子类，这样你就可以得到错误，如果你还没有错误的话。您需要的只是子类中的以下内容。
@implementation OSManagedDocument
- (id)contentsForType:(NSString *)typeName error:(NSError *__autoreleasing *)outError
{
LOG(@"Auto-Saving Document");
return [super contentsForType:typeName error:outError];
}
- (void)handleError:(NSError *)error userInteractionPermitted:(BOOL)userInteractionPermitted
{
FLOG(@" error: %@", error.localizedDescription);
NSArray* errors = [[error userInfo] objectForKey:NSDetailedErrorsKey];
if(errors != nil && errors.count > 0) {
for (NSError *error in errors) {
FLOG(@" Error: %@", error.userInfo);
}
} else {
FLOG(@" error.userInfo = %@", error.userInfo);
}
}
@end
这是获取设备上/ Documents目录的方法。文件名将附加到此路径。
- (NSURL*)documentsDirectoryURL
{
_dataDirectoryURL = [NSURL fileURLWithPath:NSHomeDirectory() isDirectory:YES];
return [_dataDirectoryURL URLByAppendingPathComponent:@"Documents"];
}
以下是指向更多信息http://ossh.com.au/design-and-technology/software-development/uimanageddocument-icloud-integration/
的链接