xcode 神奇的记录在后台保存
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Magical Record save in background
提问by Linus
I'm using the Magical Record framework to save user settings. Now, for the first time, I want to save things in a background thread. On Magical Record's github page is an example snippet I don't fully understand:
我正在使用 Magical Record 框架来保存用户设置。现在，我第一次想在后台线程中保存内容。在 Magical Record 的 github 页面上有一个我不完全理解的示例片段：
Person *person = ...;
[MagicalRecord saveInBackgroundWithBlock:^(NSManagedObjectContext *localContext){
Person *localPerson = [person MR_inContext:localContext];
localPerson.firstName = @"John";
localPerson.lastName = @"Appleseed";
}];
Why is the first line needed? Can't I just completely create the Person in the block? Thank you!
为什么需要第一行？我不能在块中完全创建 Person 吗？谢谢！
回答by Alladinian
Of course you can. This example just grabs a personobject from the outer context (your default one or whatever) and gives you a pointer to it in the localContextso you can update it in the background. If you were to create a personfrom scratch you could do something like this:
当然可以。这个示例只是person从外部上下文（您的默认上下文或其他上下文）中获取一个对象，并在 中为您提供一个指向它的指针，localContext以便您可以在后台更新它。如果您要person从头开始创建一个，您可以执行以下操作：
[MagicalRecord saveInBackgroundWithBlock:^(NSManagedObjectContext *localContext){
Person *localPerson = [Person MR_createInContext:localContext];
localPerson.firstName = @"John";
localPerson.lastName = @"Appleseed";
}];
And you're done.
你已经完成了。
PS. Note that MR_createInContext:is a class method called on Personclass (instead of MR_inContext:instance method which is called on personinstance).
附注。请注意，这MR_createInContext:是在类上调用的类方法Person（而不是在MR_inContext:实例上调用的实例方法person）。
回答by Stephan Michels
Yes, you can create the Person also in the block. The inContext: method is only necessary if you fetch for example a Person from a different context. Beware, if you create the Person in the block, then you should use the createInContext: method.
是的，您也可以在块中创建 Person。仅当您从不同的上下文中获取例如 Person 时，才需要 inContext: 方法。请注意，如果您在块中创建 Person，那么您应该使用 createInContext: 方法。
回答by Priya Thiagarajan
Magical Record save and fetch are Context-Based. So, You can either create a record in the default context or create record in a new context using MR_createInContext method. But, while fetching the records, the context should be the same as you created.
Magical Record 保存和获取是基于上下文的。因此，您可以使用 MR_createInContext 方法在默认上下文中创建记录或在新上下文中创建记录。但是，在获取记录时，上下文应该与您创建的相同。
http://pthiaga.blogspot.in/2014/11/running-database-fetch-core-data-in.html
http://pthiaga.blogspot.in/2014/11/running-database-fetch-core-data-in.html
