问+[NSManagedObjectModel mergedModelFromBundles::forStoreMetadata:]总是返回零

EN

    NSDictionary* storeHashes = [sourceMetadata objectForKey: NSStoreModelVersionHashesKey];
    NSArray<NSURL*>* urls = [self getModelURLs];
    urls = [urls sortedArrayUsingComparator:
                    ^NSComparisonResult(id  _Nonnull obj1, id  _Nonnull obj2)
                    {
                            NSURL* s2 = obj1;
                            NSURL* s1 = obj2;
                            return [s1.lastPathComponent compare: s2.lastPathComponent options: NSNumericSearch];
                    }];

    for (NSURL* url in urls)
    {
        NSDictionary* modelHashes = [self getHashesForModelAtURL: url];

        //  Compare the hashes…

        bool matches = true;
        for (NSString* entityKey in storeHashes.allKeys)
        {
            NSString* storeHash = storeHashes[entityKey];
            NSString* modelHash = modelHashes[entityKey];
            if (![storeHash isEqual: modelHash])
            {
                NSLogDebug(@"Model %@ has mismatch on %@", url.lastPathComponent, entityKey);
                matches = false;
            }
        }

        if (matches)
        {
            NSLogDebug(@"Version matches: %@", url.lastPathComponent);
            break;
        }
    }

- (NSArray<NSURL*>*)
getModelURLs
{
    NSBundle* bundle = [NSBundle bundleForClass: [self class]];
    NSArray<NSURL*>* urls = [bundle URLsForResourcesWithExtension: @"mom" subdirectory: @"Model.momd"];
    return urls;
}

- (NSDictionary*)
getHashesForModelAtURL: (NSURL*) inURL
{
    NSManagedObjectModel* model = [[NSManagedObjectModel alloc] initWithContentsOfURL: inURL];
    NSDictionary* hashes = model.entityVersionHashesByName;
    return hashes;
}