相关疑难解决方法(0)

我正在尝试统一模型文件中特定类的所有函数.例如,我在模型'Contact.h/Contact.m'中有一个函数fetchContactWithName:(NSString*)name,我的viewcontroller随后会调用它.

在这种情况下,将AppDelegate.h文件导入到模型文件中是不是一个坏主意,因为我需要访问它的managedObjectContext？

#import "AppDelegate.h"

@implementation Contact

...

+ (Contact *) fetchContactWithName:(NSString *) name {
  AppDelegate *delegate = (AppDelegate*)[[UIApplication sharedApplication] delegate];

  NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
  NSEntityDescription *entity = [NSEntityDescription entityForName:@"Contact" inManagedObjectContext:delegate.managedObjectContext];
  [fetchRequest setEntity:entity];

  NSPredicate *predicate = [NSPredicate predicateWithFormat:@"name == %@", name];
  [fetchRequest setPredicate:predicate];

  NSError *error = nil;
  NSArray *fetchedObjects = [delegate.managedObjectContext executeFetchRequest:fetchRequest error:&error];

  Contact *fetchedContact;
  for(Contact *contact in fetchedObjects) {
      fetchedContact = contact;
  }

  if(fetchedContact != nil) {
      return fetchedContact;
  } else {
      return nil;
  }

}
@end