关于 MagicalRecord，MR_saveNestedContexts 和 MR_save 方法有什么区别 [英] Regarding MagicalRecord, what is the difference between the methods MR_saveNestedContexts and MR_save

问题描述

在 MagicalRecord github 文档中，它指出:

In the MagicalRecord github docs it states:

MagicalRecord 提供了一个后台保存队列，以便保存所有数据在主线程外在后台执行.这表示可能需要使用 MR_saveNestedContexts 而不是典型的 MR_save 方法，以便将您的更改一直保存到您的持久存储.

MagicalRecord provides a background saving queue so that saving all data is performed off the main thread, in the background. This means that it may be necessary to use MR_saveNestedContexts rather than the typical MR_save method in order to persist your changes all the way to your persistent store.

看源码，我想不出这两种方法减去dispatch_async命令的区别.我看到他们都将所有嵌套的上下文保存到根目录，因此持久保存到商店.但是为什么以及在什么情况下我会使用一种而不是另一种?

looking at the source, I can't figure out the difference between these two methods minus the dispatch_async command. I see that they both save all nested contexts up to the root, therefore persisting to the store. But why and in what situation would I use one over the other?

此外，只要将嵌套上下文保存到一级(不坚持存储)，我假设我仍然会使用 NSManagedObjectContext 的 - (BOOL)save:(NSError **)error方法?

Also, as far as just saving a nested context up one level (without persisting to store) I'm assuming I would still use NSManagedObjectContext's - (BOOL)save:(NSError **)error method?

以下是两种方法的源码.

Below is the source code of the two methods.

- (void) MR_save {
    [self MR_saveErrorHandler:nil];
}

- (void) MR_saveErrorHandler:(void (^)(NSError *))errorCallback {
    [self performBlockAndWait:^{
        [self MR_saveWithErrorCallback:errorCallback];

        if (self.parentContext) {
            [[self parentContext] performBlockAndWait:^{
                [[self parentContext] MR_saveErrorHandler:errorCallback];
            }];
        }
    }];
}

- (void) MR_saveNestedContexts {
    [self MR_saveNestedContextsErrorHandler:nil];
}

- (void) MR_saveNestedContextsErrorHandler:(void (^)(NSError *))errorCallback {
    [self MR_saveNestedContextsErrorHandler:nil completion:nil];
}

- (void) MR_saveNestedContextsErrorHandler:(void (^)(NSError *))errorCallback completion:(void (^)(void))completion {
    [self performBlock:^{
        [self MR_saveWithErrorCallback:errorCallback];

        if (self.parentContext) {
            [[self parentContext] performBlock:^{
                [[self parentContext] MR_saveNestedContextsErrorHandler:errorCallback completion:completion];
            }];
        } else {
            if (completion) {
                dispatch_async(dispatch_get_main_queue(), ^{
                    completion();
                });
            }
        }
    }];
}

推荐答案

'MR_save' 和 'MR_saveNestedContexts' 之间的相似性在 2.0.8 版本中发生了变化(我使用的是 2.0.7).

The similarity between 'MR_save' and 'MR_saveNestedContexts' was changed in version 2.0.8 (I was using 2.0.7).

这是 github 上的提交:https://github.com/magicalpanda/MagicalRecord/commit/f7c4350e9daf7d90eec83ba5eafeccfa7af34312

Here is the commit on github: https://github.com/magicalpanda/MagicalRecord/commit/f7c4350e9daf7d90eec83ba5eafeccfa7af34312

以及讨论:https://github.com/magicalpanda/MagicalRecord/issues/305

总而言之，在 2.0.8 版本中，'MR_save' 现在只保存当前上下文，'MR_saveNestedContexts' 递归地保存到最顶层的上下文.

So to summarize, in version 2.0.8, 'MR_save' now only saves the current context, and 'MR_saveNestedContexts' recursively saves up to the topmost context.

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