将管理对象从xml插入Core数据

Question

这是我第一次尝试完成核心数据，并且遇到了一些问题。我的应用程序中有一个xml解析器，我一直在尝试将所有信息添加到核心数据中，但在启动时一直崩溃。我将我的核心数据设置为1个实体作为“主题”。在那个实体中，我有15个属性。下面是我创建.CoreData后为ManagedObject创建的自动文件xcode。

    Themes.h

    #import <Foundation/Foundation.h>
    #import <CoreData/CoreData.h>


    @interface Themes : NSManagedObject

    @property (nonatomic, retain) NSString * themeName;
    @property (nonatomic, retain) NSString * themeArtist;
    @property (nonatomic, retain) NSString * themeImage;
    @property (nonatomic, retain) NSString * themeDescription;
    @property (nonatomic, retain) NSString * twitterName;
    @property (nonatomic, retain) NSString * themePrice;
    @property (nonatomic, retain) NSString * screenshots;
    @property (nonatomic, retain) NSString * cydiaLink;
    @property (nonatomic, retain) NSString * themeVersion;
    @property (nonatomic, retain) NSString * deciption;
    @property (nonatomic, retain) NSString * repo;
    @property (nonatomic, retain) NSString * hd;
    @property (nonatomic, retain) NSString * sd;
    @property (nonatomic, retain) NSString * ipad;

    @end



#import "Themes.h"


@implementation Themes

@dynamic themeName;
@dynamic themeArtist;
@dynamic themeImage;
@dynamic themeDescription;
@dynamic twitterName;
@dynamic themePrice;
@dynamic screenshots;
@dynamic cydiaLink;
@dynamic themeVersion;
@dynamic deciption;
@dynamic repo;
@dynamic hd;
@dynamic sd;
@dynamic ipad;

-(void)setThemeName:(NSString *)themeName{

self.themeName = [themeName copy];


}



@end

这是我的xml Parser文件，其中应该发生所有魔法。总的来说，一切都很好用我的解析器，就在我做的时候

“themesObjects =（主题*）[NSEntityDescription
    insertNewObjectForEntityForName：themesObjects.themeName“
    inManagedObjectContext：managedObjectContext];“

应用程序将崩溃我假设因为我没有正确地将对象插入到coredata中。

#import <Foundation/Foundation.h>
#import "ThemeParseObject.h"
#import "Themes.h"


@class ThemeParseObject;

@interface ThemeXMLParser : NSObject <NSXMLParserDelegate>  {

 NSMutableData *recivedData;
 NSMutableArray *themes;
 NSMutableString    *currentNodeContent;
 NSXMLParser        *parser;

Themes *themesObjects;
NSManagedObjectContext *managedObjectContext;  
NSMutableArray *themeArray;   

ThemeParseObject *currentTheme;

}
@property (readonly, retain) NSMutableArray *themes;
@property (nonatomic, retain) NSManagedObjectContext *managedObjectContext;  
@property (nonatomic, retain) NSMutableArray *themeArray;   


-(id) loadXMLByURL:(NSString *)urlString;

@end


#import "ThemeXMLParser.h"


@implementation ThemeXMLParser

@synthesize themes;
@synthesize managedObjectContext;
@synthesize themeArray;



-(id) loadXMLByURL:(NSString *)urlString{


themesObjects = [[Themes alloc]init];
managedObjectContext = [[NSManagedObjectContext alloc] init];
themes          = [[NSMutableArray alloc] init];
NSURL *url      = [NSURL URLWithString:urlString];
NSData  *data   = [[NSData alloc] initWithContentsOfURL:url];
parser          = [[NSXMLParser alloc] initWithData:data];
parser.delegate = self;
[parser parse];
return self;    

}

- (void) parser:(NSXMLParser *)parser didStartElement:(NSString *)elementname   
namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName 
attributes:(NSDictionary *)attributeDict
{


if ([elementname isEqualToString:@"theme"]) 
{
    currentTheme = [ThemeParseObject alloc];
}
}


- (void) parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName     
namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName
{  



NSManagedObjectContext *context = [self managedObjectContext];
NSManagedObject *ObjectsToInsert = [NSEntityDescription
                                 insertNewObjectForEntityForName:@"Themes" 
                                 inManagedObjectContext:context];    

if ([elementName isEqualToString:@"name"]) {

    currentTheme.themeNameString = currentNodeContent;

    themesObjects.themeName = currentTheme.themeNameString;

    [ObjectsToInsert setValue:themesObjects.themeName forKey:@"themeName"];


}
if ([elementName isEqualToString:@"creator"]) {

    currentTheme.themeCreator = currentNodeContent;
   // themesObjects = (Themes *)[NSEntityDescription 
insertNewObjectForEntityForName:@"themeArtist" 
inManagedObjectContext:managedObjectContext];  


}    
if ([elementName isEqualToString:@"price"]) {

    currentTheme.themePrice = currentNodeContent;
    //themesObjects = (Themes *)[NSEntityDescription 
insertNewObjectForEntityForName:@"themePrice" 
inManagedObjectContext:managedObjectContext];  


}      
if ([elementName isEqualToString:@"twitter"]) {

    currentTheme.creatorTwitterName = currentNodeContent;
    //themesObjects = (Themes *)[NSEntityDescription 
insertNewObjectForEntityForName:@"twitterName"   
inManagedObjectContext:managedObjectContext];  


}  
if ([elementName isEqualToString:@"link"]) {

    currentTheme.cydiaLink = currentNodeContent;
    //themesObjects = (Themes *)[NSEntityDescription 
insertNewObjectForEntityForName:@"cydiaLink" 
inManagedObjectContext:managedObjectContext];  

}   
if ([elementName isEqualToString:@"deciption"]) {

    currentTheme.deciption = currentNodeContent;
    //themesObjects = (Themes *)[NSEntityDescription 
insertNewObjectForEntityForName:@"deciption"   
inManagedObjectContext:managedObjectContext];  

}     

if ([elementName isEqualToString:@"screenshots"]) {

    currentTheme.screenShots = currentNodeContent;

}        
if ([elementName isEqualToString:@"promo"]) {

    currentTheme.tblViewImage = currentNodeContent;
} 

if ([elementName isEqualToString:@"description"]) {

    currentTheme.themeDescription = currentNodeContent;

}     

if ([elementName isEqualToString:@"version"]) {

    currentTheme.themeVersion = currentNodeContent;

  //   NSLog(@"version: %@", currentNodeContent);        
}       

if ([elementName isEqualToString:@"repo"]) {

    currentTheme.themeRepo = currentNodeContent;

   // NSLog(@"repo: %@", currentNodeContent);

}       

if ([elementName isEqualToString:@"HD"]) {

    currentTheme.HD = currentNodeContent;

  //  NSLog(@"HD: %@", currentNodeContent);

}     

if ([elementName isEqualToString:@"SD"]) {

    currentTheme.SD = currentNodeContent;

   // NSLog(@"SD: %@", currentNodeContent);

}   

if ([elementName isEqualToString:@"iPad"]) {

    currentTheme.ipad = currentNodeContent;

    //NSLog(@"iPad: %@", currentNodeContent);

}       

if ([elementName isEqualToString:@"iPhoneScreenshots"]) {

    currentTheme.fullScreenShots = currentNodeContent;
   // themesObjects = (Themes *)[NSEntityDescription   
insertNewObjectForEntityForName:@"screenshots"   
inManagedObjectContext:managedObjectContext];         
  //  NSLog(@"fullScreenShots: %@", currentNodeContent);

    }     

    if ([elementName isEqualToString:@"theme"]) 
{

    [themes addObject:currentTheme];
    [currentTheme release];
    currentTheme = nil;
    [currentNodeContent release];
    currentNodeContent = nil;

}


}

- (void) parser:(NSXMLParser *)parser foundCharacters:(NSString *)string
{
currentNodeContent = (NSMutableString *) [string    
stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];
}

这是应用崩溃时记录的内容

2012-01-06 08:02:18.619 ThemeCatcher[2667:207] CoreData: error: Failed to call   
designated initializer on NSManagedObject class 'Themes' 
2012-01-06 08:02:19.000 ThemeCatcher[2667:207] -[Themes themeName]: unrecognized   
selector sent to instance 0x87072d0

如果有人有任何建议或想法，我可以从这里去，那将是非常棒的。如果这看起来好像很多代码，我很抱歉，但我觉得让别人知道代码里面究竟发生了什么是非常的...谢谢你，我非常感谢任何帮助！

Answer 1

themesObjects = [[Themes alloc]init];
managedObjectContext = [[NSManagedObjectContext alloc] init];

我认为这两行有两个错误。首先，您没有在主题初始化程序中使用NSManagedObject的指定初始化程序。我知道这有两个原因：a）这正是错误信息所说的; b）初始化程序无法知道要使用的上下文，因为您尚未在该点创建上下文。 designated initializer for NSManagedObjectContext是：

-initWithEntity:insertIntoManagedObjectContext:

但是，通常的做法是使用NSEntityDescription的+ insertNewObjectForEntityForName:inManagedObjectContext:便捷方法来创建新对象并将其添加到上下文中。无论哪种方式，您都需要使用其中之一。

第二个问题是，在创建Themes对象时，您没有托管对象上下文，并且在创建它时，您似乎没有正确设置上下文。您应该在创建后为上下文设置持久性存储协调器。

更新：第三个问题是当你写：

themesObjects = (Themes *)[NSEntityDescription insertNewObjectForEntityForName:themesObjects.themeName" inManagedObjectContext:managedObjectContext];

您需要确保模型具有与themeObjects.themeName的值匹配的实体。使用从XML文件获取的数据来确定主题名称是不常见的，因为XML文件中的错误会导致错误，并且还因为它将XML的结构与核心数据模型紧密联系在一起。确保您不会将 XML实体的概念与核心数据实体混淆 - 这是两回事。核心数据实体是模型中不同类型的对象;例如，你可能有一个主题实体。