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我试图更新核心数据中的某些记录。我米采用以下步骤来完成它更新核心数据记录<fault>
- 获取与谓词函数从核心数据
- 将结果存储在一个对象数组
- 遍历数组设置检索记录并更新每个记录
- 呼叫保存上下文
余米运行到两个问题
- 初始运行后,我得到<故障>在日志中
- 我不能确定是否保存上下文将保存对象
我的代码:
- (void)fetchExpenses {
// Define our table/entity to use
NSEntityDescription *entity = [NSEntityDescription entityForName:@"Expense" inManagedObjectContext:managedObjectContext];
// Setup the fetch request
NSFetchRequest *request = [[NSFetchRequest alloc] init];
[request setEntity:entity];
// Define how we will sort the records
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"timestamp" ascending:NO];
NSArray *sortDescriptors = [NSArray arrayWithObject:sortDescriptor];
[request setSortDescriptors:sortDescriptors];
[sortDescriptor release];
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"publishTimestamp == nil"];
[request setPredicate:predicate];
// Fetch the records and handle an error
NSError *error;
NSMutableArray *mutableFetchResults = [[managedObjectContext executeFetchRequest:request error:&error] mutableCopy];
if (!mutableFetchResults) {
// Handle the error.
// This is a serious error and should advise the user to restart the application
}
// Save our fetched data to an array
[self setExpenseArray: mutableFetchResults];
[mutableFetchResults release];
[request release];
}
- (void) save: {
[self fetchExpenses];
int i = 1;
int max = [expenseArray count];
for(i=1; i<=max; i++) {
// Get the expense selected.
Expense *expense = [expenseArray objectAtIndex: i];
// Do your updates here
[expense setTimestamp:2]
}
}
Thanks TechZen如果我在Array中存储fetchResults并对Array进行更改,然后调用save将它存储在核心数据中的数据? –
是的,这是管理对象的“管理”部分。针对上下文的提取返回由上下文管理的对象,上下文保存对对象的所有更改。 – TechZen