我正在为 ios 5.1 开发一个 xcode 4.3 版本的 coredata 项目。我创建了一个 ARC 空项目，选中了 CoreData 复选框，遵循 xcode 添加的方法来管理模型并由我按照将预填充 sqllite db 复制到我的应用程序的教程进行修改，预填充 db 位于项目文件夹内的资源组中并且具有相同的模型和项目名称。
- (void)saveContext
{
NSError *error = nil;
NSManagedObjectContext *managedObjectContext = self.managedObjectContext;
if (managedObjectContext != nil) {
if ([managedObjectContext hasChanges] && ![managedObjectContext save:&error]) {
// Replace this implementation with code to handle the error appropriately.
// abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
abort();
}
}
}
#pragma mark - Core Data stack
// Returns the managed object context for the application.
// If the context doesn't already exist, it is created and bound to the persistent store coordinator for the application.
- (NSManagedObjectContext *)managedObjectContext
{
if (_managedObjectContext != nil) {
return _managedObjectContext;
}
NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator];
if (coordinator != nil) {
_managedObjectContext = [[NSManagedObjectContext alloc] init];
[_managedObjectContext setPersistentStoreCoordinator:coordinator];
}
return _managedObjectContext;
}
// Returns the managed object model for the application.
// If the model doesn't already exist, it is created from the application's model.
- (NSManagedObjectModel *)managedObjectModel
{
if (_managedObjectModel != nil) {
return _managedObjectModel;
}
NSURL *modelURL = [[NSBundle mainBundle] URLForResource:@"Prova1" withExtension:@"momd"];
NSLog(@"modelURL %@",modelURL);
_managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelURL];
return _managedObjectModel;
}
// Returns the persistent store coordinator for the application.
// If the coordinator doesn't already exist, it is created and the application's store added to it.
- (NSPersistentStoreCoordinator *)persistentStoreCoordinator
{
if (_persistentStoreCoordinator != nil) {
return _persistentStoreCoordinator;
}
NSString *storePath = [[[self applicationDocumentsDirectory] absoluteString] stringByAppendingPathComponent:@"Prova1.sqlite"];
NSLog(@"storePath %@",storePath);
NSURL *storeURL = [NSURL fileURLWithPath:storePath];
NSLog(@"storeURL %@",storeURL);
// Put down default db if it doesn't already exist
NSFileManager *fileManager = [NSFileManager defaultManager];
if (![fileManager fileExistsAtPath:storePath]) {
NSString *defaultStorePath = [[NSBundle mainBundle] pathForResource:@"Prova1" ofType:@"sqlite"];
if (defaultStorePath) {
[fileManager copyItemAtPath:defaultStorePath toPath:storePath error:NULL];
}
}/**/
/*NSURL *storeURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:@"Prova1.sqlite"];*/
NSError *error = nil;
_persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];
if (![_persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:nil error:&error]) {
/*
Replace this implementation with code to handle the error appropriately.
abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
Typical reasons for an error here include:
* The persistent store is not accessible;
* The schema for the persistent store is incompatible with current managed object model.
Check the error message to determine what the actual problem was.
If the persistent store is not accessible, there is typically something wrong with the file path. Often, a file URL is pointing into the application's resources directory instead of a writeable directory.
If you encounter schema incompatibility errors during development, you can reduce their frequency by:
* Simply deleting the existing store:
[[NSFileManager defaultManager] removeItemAtURL:storeURL error:nil]
* Performing automatic lightweight migration by passing the following dictionary as the options parameter:
@{NSMigratePersistentStoresAutomaticallyOption:@YES, NSInferMappingModelAutomaticallyOption:@YES}
Lightweight migration will only work for a limited set of schema changes; consult "Core Data Model Versioning and Data Migration Programming Guide" for details.
*/
NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
abort();
}
return _persistentStoreCoordinator;
}
#pragma mark - Application's Documents directory
// Returns the URL to the application's Documents directory.
- (NSURL *)applicationDocumentsDirectory
{
return [[[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask] lastObject];
}
在这里，viewcontroller 的实现带有一些与 db 交互的字段。
@implementation ALCViewController
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
// Custom initialization
}
return self;
}
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view.
self.textfied1 = [[UITextField alloc] initWithFrame:CGRectMake(200, 50, 300, 30)];
self.textfied1.borderStyle = UITextBorderStyleRoundedRect;
self.textfied1.delegate = self;
[self.view addSubview:self.textfied1];
self.textfied2 = [[UITextField alloc] initWithFrame:CGRectMake(200, 100, 300, 30)];
self.textfied2.borderStyle = UITextBorderStyleRoundedRect;
self.textfied2.delegate = self;
[self.view addSubview:self.textfied2];
self.salvaButton = [UIButton buttonWithType:UIButtonTypeRoundedRect];
[self.salvaButton setFrame:CGRectMake(200, 150, 100, 20)];
[self.salvaButton setTitle:@"salva" forState:UIControlStateNormal];
[self.salvaButton addTarget:self action:@selector(salva:) forControlEvents:UIControlEventTouchDown];
[self.view addSubview:self.salvaButton];
self.cercaButton = [UIButton buttonWithType:UIButtonTypeRoundedRect];
[self.cercaButton setFrame:CGRectMake(200, 200, 100, 20)];
[self.cercaButton setTitle:@"Elenca" forState:UIControlStateNormal];
[self.cercaButton addTarget:self action:@selector(cerca:) forControlEvents:UIControlEventTouchDown];
[self.view addSubview:self.cercaButton];
}
- (void)viewDidUnload
{
[super viewDidUnload];
// Release any retained subviews of the main view.
}
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
return (interfaceOrientation == UIInterfaceOrientationPortrait);
}
- (BOOL)textFieldShouldBeginEditing:(UITextField *)textField {
UIToolbar *toolbar = [[UIToolbar alloc] init];
[toolbar setBarStyle:UIBarStyleBlackTranslucent];
[toolbar sizeToFit];
UIBarButtonItem *doneButton = [[UIBarButtonItem alloc] initWithTitle:@"Done" style:UIBarButtonItemStyleDone target:self action:@selector(doneClicked:)];
if ([textField isEqual:self.textfied1]) {
[doneButton setTag:1];
}
if ([textField isEqual:self.textfied2]) {
[doneButton setTag:2];
}
[toolbar setItems:[NSArray arrayWithObjects:/*flexibleSpaceLeft,*/ doneButton, nil]];
[textField setInputAccessoryView:toolbar];
[textField setText:@""];
[textField setTextColor:[UIColor blackColor]];
[textField setFont:[UIFont systemFontOfSize:16]];/**/
return YES;
}
- (void)doneClicked:(id)sender {
UIButton *bSender = (UIButton *)sender;
switch ([bSender tag]) {
case 1: {
[self.textfied1 resignFirstResponder];
}
break;
case 2: {
[self.textfied2 resignFirstResponder];
}
break;
default:
break;
}
}
- (void)salva:(id)sender {
ALCAppDelegate *appDelegate = [[UIApplication sharedApplication] delegate];
NSManagedObjectContext *context = [appDelegate managedObjectContext];
NSManagedObject *newContact;
newContact = [NSEntityDescription insertNewObjectForEntityForName:@"Stica" inManagedObjectContext:context];
[newContact setValue:self.textfied1.text forKey:@"nome"];
[newContact setValue:self.textfied2.text forKey:@"sfiga"];
self.textfied1.text = @"";
self.textfied2.text = @"";
NSError *error;
[context save:&error];
//status.text = @”Contact saved”;
}
- (void)cerca:(id)sender {
ALCAppDelegate *appDelegate = [[UIApplication sharedApplication] delegate];
NSManagedObjectContext *context = [appDelegate managedObjectContext];
NSEntityDescription *entityDesc = [NSEntityDescription entityForName:@"Stica" inManagedObjectContext:context];
NSFetchRequest *request = [[NSFetchRequest alloc] init];
[request setEntity:entityDesc];
/*NSPredicate *pred = [NSPredicate predicateWithFormat:@"(name = %@)", name.text];
[request setPredicate:pred];*/
NSError *error;
NSArray *objects = [context executeFetchRequest:request error:&error];
if ([objects count] == 0) {
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Risultati" message:@"Vuoto" delegate:self cancelButtonTitle:@"Ok" otherButtonTitles:nil];
[alert show];
}
else {
for (NSManagedObject *object in objects) {
NSMutableString *string = [[NSMutableString alloc] initWithFormat:@"%@ - %@",[object valueForKey:@"nome"],[object valueForKey:@"sfiga"]];
NSLog(@"%@",string);
}
}
}
@end
当我尝试查看存储在数据库中的记录时，问题就来了，实际上是按下名为“Elenca”的按钮的错误，xcode 给了我这个错误：
Unresolved error Error Domain=NSCocoaErrorDomain Code=512
"The operation couldn’t be completed. (Cocoa error 512.)"
UserInfo=0x6e7a120 {
reason=Failed to create file; code = 2
},
{
reason = "Failed to create file; code = 2";
}
我也尝试输出一些变量：
storePath文件：/localhost/Users/winimac01/Library/Application%20Support/iPhone%20Simulator/5.1/Applications/7733DC6C-CE52-4EB4-9A60-26962F7AEDD9/Documents/Prova1.sqlite
storeURL文件：/localhost/Users/winimac01/Library/Application%2520Support/iPhone%2520Simulator/5.1/Applications/7733DC6C-CE52-4EB4-9A60-26962F7AEDD9/Documents/Prova1.sqlite -- file://localhost/
型号网址attributeType 700 , attributeValueClassName NSString, defaultValue (null)\";\n nome = \"(), name nome, isOptional 1, isTransient 0, entity Meco, renamingIdentifier nome, 验证谓词 (\n), 警告 (\n), versionHashModifier (null)\n userInfo {\n}, attributeType 700, attributeValueClassName NSString, defaultValue (null)\";\n relationship = \"(), name 关系, isOptional 1, isTransient 0, entity Meco, renamingIdentifier 关系, 验证谓词 (\n), 警告 (\n), versionHashModifier (null)\n userInfo {\n}, 目标实体 Stica, inverseRelationship 关系, minCount 1, maxCount 1, isOrdered 0, deleteRule 1\";\n}, 子实体(null), userInfo {\n}, versionHashModifier (null)"; Stica = "() 名称 Stica, managedObjectClassName NSManagedObject, renamingIdentifier Stica, attributeType 700 , attributeValueClassName NSString, defaultValue (null)\";\n}, subentities (null), userInfo {\n}, versionHashModifier (null)"; }, 获取请求模板 { }
而且我不知道为什么storeURL有这种形式，字符串末尾的“--file://localhost/”是什么？为什么不能创建 .sqlite 文件？什么是解决问题的正确方法？我已经尝试重置模拟器并且路径是正确的......
提前致谢
编辑1： 我学过的就是这个
edit2： 一个可行的解决方案是更改这段代码：
NSString *storePath = [[[self applicationDocumentsDirectory] absoluteString] stringByAppendingPathComponent:@"Prova1.sqlite"];
NSURL *storeURL = [NSURL fileURLWithPath:storePath];
// Put down default db if it doesn't already exist
NSFileManager *fileManager = [NSFileManager defaultManager];
if (![fileManager fileExistsAtPath:storePath]) {
NSString *defaultStorePath = [[NSBundle mainBundle] pathForResource:@"Prova1" ofType:@"sqlite"];
if (defaultStorePath) {
[fileManager copyItemAtPath:defaultStorePath toPath:storePath error:NULL];
}
}/**/
和：
NSURL *storeURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:@"Prova1.sqlite"];
// Put down default db if it doesn't already exist
NSFileManager *fileManager = [NSFileManager defaultManager];
if (![fileManager fileExistsAtPath:storePath]) {
NSURL *defaultStoreURL = [[NSBundle mainBundle] URLForResource:@"Prova1" withExtension:@"sqlite"];
if (defaultStoreURL) {
[fileManager copyItemAtURL:defaultStoreURL toURL:storeURL error:NULL];
}
}/**/