根据要求将应用程序数据与iCloud同步

Question

I want to store some of my application data in iCloud, and I want it to be saved when the application is going to the background or is shut down.

I have a MyDocument class, which is written in accordance with this Apple tutorial . In fact, I do this:

// this function called from applicationDidEnterBackground
void SaveICloudData( const char *rawData )
{
    MyDocument *doc = AppDelegate.getICloudDocument;     // MyDocument is subclass of UIDocument, like in tutorial

    NSString *str = [[NSString alloc] initWithUTF8String:rawData];
    [doc setDocumentText:str];
}

My app goes to the background and is synchronized only when I turn it on again. But I want to synchronize my data with iCloud manually. How can I do this?

Answer 1

Before exiting, UIDocument checks if the document hasUnsavedChanges . If YES , saving is invoked.
You are setting the document text in the applicationDidEnterBackground delegate method, which is probably too late.

From the method docs:

You should perform any tasks relating to adjusting your user interface before this method exits but other tasks (such as saving state) should be moved to a concurrent dispatch queue or secondary thread as needed. Because it's likely any background tasks you start in applicationDidEnterBackground: will not run until after that method exits, you should request additional background execution time before starting those tasks. In other words, first call beginBackgroundTaskWithExpirationHandler: and then run the task on a dispatch queue or secondary thread.