如何更新核心数据中已有的对象？
如何更新核心数据中已有的对象？
提问于 2012-05-13 20:39:29
当我插入新对象时，我会使用以下代码：
NSManagedObjectContext *context = [appDelegate managedObjectContext];
Favorits *favorits = [NSEntityDescription insertNewObjectForEntityForName:@"Favorits" inManagedObjectContext:context];
favorits.title = @"Some title";
NSError *error;
if (![context save:&error]) {
NSLog(@"Whoops");
}如何更新核心数据中的现有对象？
回答 4
Stack Overflow用户
发布于 2012-05-13 21:16:56
您必须从上下文中fetch对象，更改所需的属性，然后保存示例中的上下文。
Stack Overflow用户
发布于 2015-07-25 14:28:42
我希望这对你有帮助，因为它对我很有效。
NSMutableArray *results = [[NSMutableArray alloc]init];
int flag=0;
NSPredicate *pred;
if (self.txtCourseNo.text.length > 0) {
pred = [NSPredicate predicateWithFormat:@"courseno CONTAINS[cd] %@", self.txtCourseNo.text];
flag=1;
} else {
flag=0;
NSLog(@"Enter Corect Course number");
}
if (flag == 1) {
NSLog(@"predicate: %@",pred);
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc]initWithEntityName:@"Course"];
[fetchRequest setPredicate:pred];
results = [[self.context executeFetchRequest:fetchRequest error:nil] mutableCopy];
if (results.count > 0) {
NSManagedObject* favoritsGrabbed = [results objectAtIndex:0];
[favoritsGrabbed setValue:self.txtCourseName.text forKey:@"coursename"];
[self.context save:nil];
[self showData];
} else {
NSLog(@"Enter Corect Course number");
}
}Stack Overflow用户
发布于 2018-05-22 12:36:44
如果你是一个敏捷的程序员，这可以帮助你：
如果要删除NSManagedObject
在我的例子中，ID是实体学生的唯一属性
/** for deleting items */
func delete(identifier: String) {
let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
let fetchRequest:NSFetchRequest<NSFetchRequestResult> = NSFetchRequest.init(entityName: "STUDENT")
let predicate = NSPredicate(format: "ID = '\(identifier)'")
fetchRequest.predicate = predicate
do
{
let object = try context.fetch(fetchRequest)
if object.count == 1
{
let objectDelete = object.first as! NSManagedObject
context.delete(objectDelete)
}
}
catch
{
print(error)
}
} 如果您想要更新NSManagedObject：
/** for updating items */
func update(identifier: String,name:String) {
let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
let fetchRequest:NSFetchRequest<NSFetchRequestResult> = NSFetchRequest.init(entityName: "STUDENT")
let predicate = NSPredicate(format: "ID = '\(identifier)'")
fetchRequest.predicate = predicate
do
{
let object = try context.fetch(fetchRequest)
if object.count == 1
{
let objectUpdate = object.first as! NSManagedObject
objectUpdate.setValue(name, forKey: "name")
do{
try context.save()
}
catch
{
print(error)
}
}
}
catch
{
print(error)
}
}页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/10571786
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