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,为此我使用UIManagedDocument
。但是,如果我尝试使用UIManagedDocument
创建文档,则文档的openWithCompletionHandler
不成功。这就是为什么我的NSManagedObjectContext
始终为nil
,并且Xcode说无法在etc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
编辑
我解决了这个问题。问题出在以下一行:NSURL *url = [[[NSFileManager defaultManager]URLsForDirectory:NSDocumentationDirectory inDomains:NSUserDomainMask]firstObject];
。我把NSDocumentationDirectory改成了NSDocumentDirectory,问题得到解决。