iphone - 警告将方法添加到核心数据的应用程序委托(delegate)中
<p><p>我使用核心数据创建了一个新项目，然后将我需要的核心数据的所有应用程序委托(delegate)代码复制到我当前的项目应用程序委托(delegate)中。</p>
<p>我的 appdelegate.m 现在看起来像这样。</p>
<pre><code>//
//AppDelegate.m
//testingcoredata
//
//Created by iMac on 18/11/11.
//Copyright (c) 2011 __MyCompanyName__. All rights reserved.
//
#import "AppDelegate.h"
#import "MasterViewController.h"
@implementation AppDelegate
@synthesize window = _window;
@synthesize managedObjectContext = __managedObjectContext;
@synthesize managedObjectModel = __managedObjectModel;
@synthesize persistentStoreCoordinator = __persistentStoreCoordinator;
@synthesize navigationController = _navigationController;
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
self.window = [ initWithFrame:[ bounds]];
// Override point for customization after application launch.
MasterViewController *masterViewController = [ initWithNibName:@"MasterViewController" bundle:nil];
self.navigationController = [ initWithRootViewController:masterViewController];
masterViewController.managedObjectContext = self.managedObjectContext;
self.window.rootViewController = self.navigationController;
;
return YES;
}
- (void)applicationWillTerminate:(UIApplication *)application
{
// Saves changes in the application's managed object context before the application terminates.
;
}
- (void)saveContext
{
NSError *error = nil;
NSManagedObjectContext *managedObjectContext = self.managedObjectContext;
if (managedObjectContext != nil)
{
if ( && !)
{
/*
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, );
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 = ;
if (coordinator != nil)
{
__managedObjectContext = [ init];
;
}
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 = [ URLForResource:@"testingcoredata" withExtension:@"momd"];
__managedObjectModel = [ 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;
}
NSURL *storeURL = [ URLByAppendingPathComponent:@"testingcoredata.sqlite"];
NSError *error = nil;
__persistentStoreCoordinator = [ initWithManagedObjectModel:];
if (!)
{
/*
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:
[ removeItemAtURL:storeURL error:nil]
* Performing automatic lightweight migration by passing the following dictionary as the options parameter:
, NSMigratePersistentStoresAutomaticallyOption, , NSInferMappingModelAutomaticallyOption, nil];
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, );
abort();
}
return __persistentStoreCoordinator;
}
#pragma mark - Application's Documents directory
/**
Returns the URL to the application's Documents directory.
*/
- (NSURL *)applicationDocumentsDirectory
{
return [[ URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask] lastObject];
}
@end
</code></pre>
<p>我的问题如下
这部分代码中的 <strong>URLForResource</strong> 是否反射(reflect)了我创建的 xcdatamodeld 的名称？</p>
<pre><code>NSURL *modelURL = [ URLForResource:@"testingcoredata" withExtension:@"momd"];
</code></pre>
<p>使用 <strong>URLByAppendingPathComponent:</strong> 我是否必须创建一个名为 Code.sqlite 的 sqlite 数据库，还是由核心数据代码自动为我创建的？</p>
<pre><code>NSURL *storeURL = [ URLByAppendingPathComponent:@"Code.sqlite"];
</code></pre>
<p>这个方法的目的到底是什么？</p>
<pre><code>applicationDocumentsDirectory
</code></pre></p>
<br><hr><h1><strong>Best Answer-推荐答案</ strong></h1><br>
<p><ol>
<li><strong>URLForResource</strong> 表示包中 momd 文件的 uri 路径。</li>
<li><strong>URLByAppendingPathComponent</strong> - 您提供的代码将创建名为 Code.sqlite 的数据库。您可以随意更改名称。</li>
<li><strong>applicationDocumentsDirectory</strong> 方法返回应用沙箱中 Documents 文件夹的路径</li>
</ol></p>
<p style="font-size: 20px;">关于iphone - 警告将方法添加到核心数据的应用程序委托(delegate)中，我们在Stack Overflow上找到一个类似的问题：
<a href="https://stackoverflow.com/questions/8175384/" rel="noreferrer noopener nofollow" style="color: red;">
https://stackoverflow.com/questions/8175384/
</a>
</p>
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