如何创建一个NSManagedObjectContext [英] how do you create a NSManagedObjectContext

问题描述

在iPhone的核心数据中，我尝试将数据保存到 NSManagedObjectContext 时遇到各种错误。

In core data for the iPhone, I was getting all sorts of errors trying to save data to a NSManagedObjectContext.

我相信我的问题都与我使用 NSManagedObjectContext 在多个线程中使用。

I believe that my issues were all to do with me using a NSManagedObjectContext that was being used in multiple threads.

所以我想创建一个新的 NSManagedObjectContext 并尝试，但我找不到示例代码只是创建一个新的实例...

So I wanted to create a new NSManagedObjectContext and try that, but I cannot find the example code to simply create a new instance...

我知道它的简单，但我真的很感谢任何帮助。

I know its simple, but I would really appreciate any help here.

注意，我看到这篇文章在苹果文档： http://developer.apple.com/ iphone / library / documentation / cocoa / conceptual / CoreDataUtilityTutorial / Articles / 05_createStack.html

Note, I have seen this article on the Apple docs: http://developer.apple.com/iphone/library/documentation/cocoa/conceptual/CoreDataUtilityTutorial/Articles/05_createStack.html

但这使用了一些我不熟悉的代码，

But this uses some code that I am not familiar with, like the XMLStore which is not supported on the iPhone, etc.

推荐答案

这是创建新上下文的代码：

this is the code to create a new context:

- (NSManagedObjectContext *)managedObjectContext {
    NSManagedObjectContext *managedObjectContext = nil;

    NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator];
    if (coordinator != nil) {
        managedObjectContext = [[NSManagedObjectContext alloc] init];
        [managedObjectContext setPersistentStoreCoordinator:coordinator];
        [managedObjectContext setUndoManager:nil];
    }
    return [managedObjectContext autorelease];
}

只需创建一个新的上下文实例，喜欢使用。

It's simply create a new instance of the context and set the store that you would like to use.

如果您有多家商店，那么您可以这样购买：

If you have multiple stores, you would go for something like that:

- (NSManagedObjectContext *)managedObjectContextForStore:(NSString *)store {
    NSManagedObjectContext *managedObjectContext = nil;

    NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinatorForStore:store];
    if (coordinator != nil) {
        managedObjectContext = [[NSManagedObjectContext alloc] init];
        [managedObjectContext setPersistentStoreCoordinator:coordinator];
        [managedObjectContext setUndoManager:nil];
    }
    return [managedObjectContext autorelease];
}

有关详情，请查看 Apple的核心数据iOS教程。

干杯！

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