你如何打印出 Core Data 对象？

Question

我想在 NSLog 语句的代码中打印出存储在 Core Data 对象中的数据。

背景信息：我正在从 PList 中读取数据以进行预填充，然后将其传输到 Core Data。发布的应用程序只会从 Core Data 中读取。

这是我的 PList 的样子：

这是我的对象图：

这是我的代码：

-(void)initXML
{
    [self deleteAllEntities:@"Recipes"];

    [self copyXMLtoEntities];

    [self printEntities];
}

_

// deletes data from all entities to ready them for pre-population
-(void)deleteAllEntities:(NSString *)entityDescription
{
    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
    NSEntityDescription *entity = [NSEntityDescription entityForName:entityDescription inManagedObjectContext:self.managedObjectContext];
    [fetchRequest setEntity:entity];

    NSError *error;
    NSArray *items = [self.managedObjectContext executeFetchRequest:fetchRequest error:&error];

    for (NSManagedObject *managedObject in items)
    {
        [self.managedObjectContext deleteObject:managedObject];
        DLog(@"%@ ..object deleted", entityDescription);
    }

    if (![self.managedObjectContext save:&error])
    {
        DLog(@"Error deleting %@ - error:%@", entityDescription, error);
    }
}

_

// This copies data from the PList to Core Data Entities, aka pre-population
-(void)copyXMLtoEntities
{        
    NSDictionary *allRecipesDictionary = [self getRecipes];
    DLog(@"allRecipes: [%@]", allRecipesDictionary);

    Recipes *recpies = [NSEntityDescription insertNewObjectForEntityForName:@"Recipes" inManagedObjectContext:self.managedObjectContext];

    for (NSString *recipeKey in allRecipesDictionary)
    {
        NSDictionary *recipeDict = [allRecipesDictionary objectForKey:recipeKey];

        Recipe *recipe = [NSEntityDescription insertNewObjectForEntityForName:@"Recipe" inManagedObjectContext:self.managedObjectContext];
        recipe.id = recipeKey;
        recipe.name = [recipeDict objectForKey:@"name"];

        NSMutableArray *contentItemsArray = [[NSMutableArray alloc] init];            

        NSArray *contentArrayToIterate = [recipeDict objectForKey:@"content"];            

        // loop through content array and add each item
        for (int i=0 ; i < [contentArrayToIterate count] ; i++)
        {
            // create text or image content items
            // add them to the array
            // create entities and add them to contentItemsArray

            NSDictionary *contentItemDict = contentArrayToIterate[i];

            NSDictionary *textItemDict = [contentItemDict objectForKey:@"textItem"];
            NSDictionary *imageItemDict = [contentItemDict objectForKey:@"imageItem"];
            NSString *sequenceStr = [contentItemDict objectForKey:@"sequence"];

            if (textItemDict != nil)
            {
                NSString *text = [textItemDict objectForKey:@"text"];
                TextItem *textItem = [NSEntityDescription insertNewObjectForEntityForName:@"TextItem" inManagedObjectContext:self.managedObjectContext];

                textItem.text = text;
                textItem.sequence = sequenceStr;

                // add entity to the array
                [contentItemsArray addObject:textItem];
            }

            if (imageItemDict != nil)
            {
                NSString *filename = [imageItemDict objectForKey:@"filename"];

                ImageItem *imageItem = [NSEntityDescription insertNewObjectForEntityForName:@"ImageItem" inManagedObjectContext:self.managedObjectContext];

                imageItem.filename = filename;
                imageItem.sequence = sequenceStr;

                // add entity to the array
                [contentItemsArray addObject:imageItem];
            }
        } // loop through content

        recipe.contentItems = [NSSet setWithArray:contentItemsArray];
        [recpies addRecipeObject:recipe];
    } // loop through recipes

    [self saveContext];
}

_

// This returns the Dictionary of Recipes
-(NSDictionary *)getRecipes
{
    NSString *path = [[NSBundle mainBundle] pathForResource:@"Recipes" ofType:@"plist"];
    NSDictionary *plist = [[NSDictionary alloc] initWithContentsOfFile:path];

    // recipes
    NSDictionary *recipes = [plist objectForKey:@"Recipes"];

    return recipes;
}

_

像这样打印字典：

DLog(@"allRecipes: [%@]", allRecipesDictionary);

给我很好的分类输出，如下所示：

allRecipes: [{
    "BLUEBERRY_PIE_001" =     {
        content =         (
                           {
                               textItem =                 {
                                   sequence = 1;
                                   text = "Mix sugar, cornstarch, salt, and cinnamon, and sprinkle over blueberries.";
                               };
                           },
                           {
                               imageItem =                 {
                                   filename = "mixIngredients.jpg";
                                   sequence = 2;
                               };
                           },
                                ...

像这样打印出核心数据实体：

DLog(@"self.recipes: [%@]", self.recipes);

或者这个：

DLog(@"| self.recipes description: [%@]", [self.recipes description]);

给我这个：

self.recipes: [(
"<Recipes: 0x9951840> (entity: Recipes; id: 0x9962730 <x-coredata://4E308A08-FB8A-44C5-887A-88C335378A14/Recipes/p2> ; data: {\n    recipe =     (\n    );\n})"

)]

我怎样才能让它看起来像字典打印输出？我能想到的最直接的方法是为每个迭代其自己的集合的实体添加一个“打印”方法。我的完整应用中有 32 个实体。我想避免每次从对象图中生成新实体时都必须编写此代码。

更有效的方法是扫描每个实体的属性并对其进行迭代。此链接显示如何为属性而不是关系执行此操作： http://iphonedevelopment.blogspot.com/2010/08/core-data-odds-and-ends.html

你如何使这种关系适用于人际关系？

Answer 1

最简单的方法是

for (Recipe *r in recipesObject.recipe) { NSLog(@"%@", r); }

你会得到一些额外的不那么漂亮的核心数据输出，但如果是用于信息或调试，应该没问题。此外，这些关系可能未完全记录。

更好的是，创建一个像prettyDescription 这样的方法，您可以在其中根据自己的喜好格式化输出。您可以将其放入 NSManagedObject 子类或（更好）其扩展中。

-(NSString*)prettyDescription {
    NSMutableString *result = [NSMutableString new];
    [result appendString:self.name];
    [result appendString:@"\n"];
    for (ContentItem *item in self.contentItems) {
        // append details from item to the result
    }
    return [NSString stringWithString:result]; // return immutable string
}

现在您可以使用

记录所有食谱

for (Recipe *r in recipesObject.recipe) { NSLog(@"%@", r.prettyDescription); }

---

注意：为了清楚起见，我认为您应该重命名实体和属性，如下所示：

Recipes          --> RecipesCollection
Recipes.recipe   --> RecipesCollection.recipes
Recipe.recipes   --> Recipe.collection