如何限制在核心数据中输入null值？ [英] How to restrict entry of null value in coredata?

问题描述

我正在开发基于XMLparsing的项目，我使用coredata来存储url。

但有些时候coredata输入的null值我不知道为什么这种类型的问题发生。

这是我试过的我的代码。

   - void）feedParserDidFinish：（MWFeedParser *）parser {
 
 
 NSFetchRequest * fetchRequest = [NSFetchRequest fetchRequestWithEntityName：@demo]; 
 
 fetchRequest.predicate = [NSPredicate predicateWithFormat：@urloffeed =％@，self.Feedlink]; 
 
 NSManagedObjectContext * context = [self managedObjectContext]; 
 
 if（[[context executeFetchRequest：fetchRequest error：NULL] count] == 0）{
 //创建一个新的托管对象
 NSManagedObject * newDevice = [NSEntityDescription insertNewObjectForEntityForName： @demoinManagedObjectContext：context]; 
 [newDevice setValue：self.Name forKey：@nameofentry]; 
 [newDevice setValue：self.WebsiteName forKey：@sitename]; 
 [newDevice setValue：self.Feedlink forKey：@urloffeed]; 
 
 NSError * error = nil; 
 //将对象保存到持久存储
 if（！[context save：& error]）{
 NSLog（@无法保存！％@％@ [error localizedDescription]）; 
} 
 
} 
  

有人请帮我解决这个问题

 <$> 
解决方案
 c $ c> #define IS_NOT_NIL_OR_NULL（value）（value！= nil&& value！= Nil&& value！= NULL&& value！=（id）[NSNull null]）
 

在核心数据中保存值之前，请检查您的值为空。

  if（[[context executeFetchRequest：fetchRequest error：NULL] count] == 0）{
 //创建一个新的托管对象
 NSManagedObject * newDevice = [NSEntityDescription insertNewObjectForEntityForName：@demoinManagedObjectContext：context]; 
 if（IS_NOT_NIL_OR_NULL（self.Name））
 {
 [newDevice setValue：self.Name forKey：@nameofentry]; 
} else 
 {
 //处理else case。在这里get self.name的值为null。 
 
} 
 
 if（IS_NOT_NIL_OR_NULL（self.WebsiteName））
 {
 [newDevice setValue：self.WebsiteName forKey：@sitename]; 
} else 
 {
 //处理else case。在这里获取self.WebsiteName值为null。 
 
} 
 
 
 if（IS_NOT_NIL_OR_NULL（self.Feedlink））
 {
 [newDevice setValue：self.Feedlink forKey：@ urloffeed]; 
} else 
 {
 //处理else case。 get self.Feedlink值为null。 
 
} 
 
 NSError * error = nil; 
 //将对象保存到持久存储
 if（！[context save：& error]）{
 NSLog（@无法保存！％@％@ [error localizedDescription]）; 
} 
 
} 
  

希望它帮助你。 p>

I am working on XMLparsing based project and I used coredata to store url .

But some time coredata enter's null value I don't know why such type of problem occurs.

Here is my code which I have tried.

- (void)feedParserDidFinish:(MWFeedParser *)parser {


    NSFetchRequest *fetchRequest = [NSFetchRequest fetchRequestWithEntityName:@"demo"];

    fetchRequest.predicate = [NSPredicate predicateWithFormat:@"urloffeed = %@", self.Feedlink];

    NSManagedObjectContext *context = [self managedObjectContext];

    if ([[context executeFetchRequest:fetchRequest error:NULL] count] == 0) {
        // Create a new managed object
        NSManagedObject *newDevice = [NSEntityDescription insertNewObjectForEntityForName:@"demo" inManagedObjectContext:context];
        [newDevice setValue:self.Name forKey:@"nameofentry"];
        [newDevice setValue:self.WebsiteName forKey:@"sitename"];
        [newDevice setValue:self.Feedlink forKey:@"urloffeed"];

        NSError *error = nil;
        // Save the object to persistent store
        if (![context save:&error]) {
            NSLog(@"Can't Save! %@ %@", error, [error localizedDescription]);
        }

    }

Someone please help me regarding this issue ?

解决方案

define macros as .

 #define IS_NOT_NIL_OR_NULL(value)           (value != nil && value != Nil && value != NULL && value != (id)[NSNull null])

Before saving the value in core data check your value for null .

if ([[context executeFetchRequest:fetchRequest error:NULL] count] == 0) {
    // Create a new managed object
    NSManagedObject *newDevice = [NSEntityDescription insertNewObjectForEntityForName:@"demo" inManagedObjectContext:context];
     if (IS_NOT_NIL_OR_NULL(self.Name))
{
    [newDevice setValue:self.Name forKey:@"nameofentry"];
} else 
 {
    // Handle else case .  get self.name value is null here .

 }

     if (IS_NOT_NIL_OR_NULL(self.WebsiteName))
{
    [newDevice setValue:self.WebsiteName forKey:@"sitename"];
} else 
 {
    // Handle else case .  get self.WebsiteName value is null here .

 }


      if (IS_NOT_NIL_OR_NULL(self.Feedlink))
{
    [newDevice setValue:self.Feedlink forKey:@"urloffeed"];
} else 
 {
    // Handle else case .  get self.Feedlink value is null here .

 }

    NSError *error = nil;
    // Save the object to persistent store
    if (![context save:&error]) {
        NSLog(@"Can't Save! %@ %@", error, [error localizedDescription]);
    }

}

Hope it help you .

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