Question

我想要读入Core Data中有一些值。我可以在“顶级”中阅读，但除了字符串和数字外，每个项目还包含字典。我无法正确阅读这些语法。

Garden and Plant是我的2个核心数据实体。 Garden和Plant都是包含自己数据的NSDictionaries。花园可以包含许多植物，特定的植物可以在许多花园中，所以有很多种关系。

这很有效：

我使用plist的花园字典在firstRun上填充我的核心数据库，从应用程序启动调用就像这样：

    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];  
    if (![defaults objectForKey:@"firstRun"])
    {
        [defaults setObject:[NSDate date] forKey:@"firstRun"];
        [[NSUserDefaults standardUserDefaults] synchronize];
        [self loadGardenDataFromPlistDictionary]; 
    }

有效。第一级将各种plist值加载到核心数据中也是如此。但是我无法加载“花园”字典中“植物”字典中包含的数据... 2级深度。换句话说，名称，细节和笔记加载...但植物没有。到目前为止，这是我的代码：

 -(void) loadGardenDataFromPlistDictionary{
// build path to plist; check Documents first, then Bundle.
NSArray *paths = NSSearchPathForDirectoriesInDomains (NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsPath = [paths objectAtIndex:0];
NSString *plistPath = [documentsPath stringByAppendingPathComponent:@"defaultGardenDictionary.plist"];
if (![[NSFileManager defaultManager] fileExistsAtPath:plistPath]) 
{
    // if not in documents, get property list from main bundle
    plistPath = [[NSBundle mainBundle] pathForResource:@"defaultGardenDictionary" ofType:@"plist"];
}

// read property list into memory as an NSData object
NSData *plistXML = [[NSFileManager defaultManager] contentsAtPath:plistPath];
NSString *errorDesc = nil;
NSPropertyListFormat format;

// convert static property list into dictionary object
NSDictionary *plistDictionary = (NSDictionary *)[NSPropertyListSerialization propertyListFromData:plistXML mutabilityOption:NSPropertyListMutableContainersAndLeaves format:&format errorDescription:&errorDesc];
if (!plistDictionary) 
{
    NSLog(@"Error reading plist: %@, format: %d", errorDesc, format);
}


NSManagedObjectContext *context = self.managedObjectContext;

[plistDictionary enumerateKeysAndObjectsWithOptions:NSEnumerationConcurrent usingBlock:^(id key, id object, BOOL *stop) {
    NSManagedObject *gardenManObj = [NSEntityDescription insertNewObjectForEntityForName:@"Garden" inManagedObjectContext:context];

    [gardenManObj setValue:[thisGardenDictionary objectForKey:@"name"] forKey:@"name"];
    [gardenManObj setValue:[thisGardenDictionary objectForKey:@"detail"] forKey:@"detail"];
    [gardenManObj setValue:[thisGardenDictionary objectForKey:@"notes"] forKey:@"notes"];
    [gardenManObj setValue:[thisGardenDictionary objectForKey:@"rating"] forKey:@"rating"];

    NSDictionary *thisGardenPlantsDictionary = [thisGardenDictionary objectForKey:@"plants"];
    NSLog(@"thisGardenPlantsDictionary contains %i dictionaries.", [thisGardenPlantsDictionary count]);
    //The trace statement above shows the correct number of plants in each garden dictionary. oooh... so tantalizingly close!

    //However, the next item is the dictionary of plants in this garden. It comes up blank. 
    //I don't understand the syntax to load that dictionary of plants into its corresponding dictionary of plants within a garden in core data. 

    //I deleted most of the things I've tried and failed with so far. Here's my last attempt:

    // the obvious and parallel:
    [gardenManObj setValue:[thisGardenDictionary objectForKey:@"plants"] forKey:@"plants"];
        //did not work; xCode compiler objected to "incompatible pointer types."

    //the compiler seemed to want an NSSet, so I tried:
    NSSet *thisGardenPlantsSet = [thisGardenDictionary mutableSetValueForKey:@"steps"];
        NSLog(@"thisGardenPlantsSet contains %i sets.", [thisGardenPlantsSet count]);
    [gardenManObj setValue:thisGardenPlantsSet forKey:@"steps"];
    //the compiler was fooled, but the setValue crashed at runtime.
 }];

}

我错过了什么？

Answer 1

您没有为每个Plant字典值创建新的托管对象。您只是尝试将字典本身分配给关系，当然，这种关系不起作用。

您需要添加以下内容：

[gardenManObj setValue:[thisGardenDictionary objectForKey:@"rating"] forKey:@"rating"];

NSDictionary *thisGardenPlantsDictionary = [thisGardenDictionary objectForKey:@"plants"];
NSLog(@"thisGardenPlantsDictionary contains %i dictionaries.", [thisGardenPlantsDictionary count]);
NSManagedObject *plantMO;
for (Plant *eachPlant in thisGardenPlantsDictionary) {
  plantMO=[NSEntityDescription insertNewObjectForEntityForName:@"Plant" inManagedObjectContext:context];
  [plantMO setValue:[eachPlant valueForKey:@"someValue" forKey:@"someKey"]];
   //... repeat for all attributes
  [plantMO setValue:gardenManObj forKey:@"gardent"];
}

...将创建必要的Plant个对象，并设置与正确的Garden对象的关系。

将plist读入核心数据 - NSDictionary中的NSDictionary

1 个答案: