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我想知道是否可以初始化 NSManagedObject 的子类？我有一个类“Actualite”，它是 NSManagedObject 的子类，当我想初始化这个类时，我收到这个错误：“CoreData：错误：无法在 NSManagedObject 类 Actualite 上调用指定的初始化程序”，并且应用程序在此消息后崩溃“-[Actualite setTitre:]: 无法识别的选择器发送到实例 0x8433be0”

这是我的代码：

-(void) recupererActualites {
listeNouvellesActualites = [[NSMutableArray alloc] init];

// Convert the supplied URL string into a usable URL object
NSURL *url = [NSURL URLWithString:FACE06_RSS];

// Create a new rssParser object based on the TouchXML "CXMLDocument" class, this is the
// object that actually grabs and processes the RSS data
CXMLDocument *rssParser = [[CXMLDocument alloc] initWithContentsOfURL:url encoding:NSUTF8StringEncoding options:0 error:nil];

// Create a new Array object to be used with the looping of the results from the rssParser
NSArray *resultNodes = NULL;

// Set the resultNodes Array to contain an object for every instance of an  node in our RSS feed
resultNodes = [rssParser nodesForXPath:@"//item" error:nil];

NSMutableArray* tmp = [[NSMutableArray alloc] init];
for (CXMLElement* resultElement in resultNodes) {
    // Create a temporary MutableDictionary to store the items fields in, which will eventually end up in blogEntries
    NSMutableDictionary *blogItem = [[NSMutableDictionary alloc] init];
    NSMutableArray* categories = [[NSMutableArray alloc] init];

    // Create a counter variable as type "int"
    int counter;

    // Loop through the children of the current  node
    for(counter = 0; counter < [resultElement childCount]; counter++) {
        // Add each field to the blogItem Dictionary with the node name as key and node value as the value
        if([[[resultElement childAtIndex:counter] name] isEqual:@"category"])
            [categories addObject:[[resultElement childAtIndex:counter] stringValue]];
        else {
            if ([[resultElement childAtIndex:counter] stringValue] != nil)
                [blogItem setObject:[[resultElement childAtIndex:counter] stringValue] forKey:[[resultElement childAtIndex:counter] name]];
            else
                [blogItem setObject:@"" forKey:[[resultElement childAtIndex:counter] name]];
        }
    }

    Actualite* actu = [[Actualite alloc] init];
    [blogItem setObject:categories forKey:@"categories"];
    [actu initWithDictionnary:blogItem];
    [tmp addObject:actu];
    //[actu release];

    [categories release];
    [blogItem release];
}
listeNouvellesActualites = tmp;

[rssParser release];
resultNodes = nil;

// Stockage des actualités en local
[self stockerActualites];
}

而 initWithDictionary 方法设置了 Actualite 类的所有属性。

我也试过

Actualite* actu = [[Actualite alloc] initWithEntity:[NSEntityDescription entityForName:@"Actualite" inManagedObjectContext:managedObjectContext] insertIntoManagedObjectContext:managedObjectContext];

和

Actualite* actu = (Actualite*)[NSEntityDescription entityForName:@"Actualite" inManagedObjectContext:managedObjectContext];

代替

Actualite* actu = [[Actualite alloc] init];

错误消失，但应用程序此时停止。我不知道我能做什么...

有人已经有这个问题了吗？

非常感谢 ！

4

1 回答 1

4

这个想法是您要求在上下文中创建一个新对象，然后使用它：

Actualite* actu = [NSEntityDescription insertNewObjectForEntityForName:@"Actualite" inManagedObjectContext:managedObjectContext];
于 2012-05-09T16:08:40.657 回答