Question

我想从“Entry”中检索单个值（String）。我相信我错过了一些东西。有人能说出来吗？

XYZAppDelegate *appDelegate = [[UIApplication sharedApplication] delegate];

NSManagedObjectContext *managedObjectContext = appDelegate.managedObjectContext;
NSFetchRequest *request = [[NSFetchRequest alloc] init]; 
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"name == %@", entryToSearchFor]; 
NSEntityDescription *entity = [NSEntityDescription entityForName:@"Entry" inManagedObjectContext:managedObjectContext]; 
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"name" ascending:NO]; 
NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil];   

[request setSortDescriptors:sortDescriptors];
[request setEntity: entity]; 
[request setPredicate: predicate]; 

NSArray *results = [managedObjectContext executeFetchRequest:request error:nil];

if (results == nil) {
    NSLog(@"No results found");     
}else {
    NSLog(@"entryToSearchFor %@", entryToSearchFor);
    NSLog(@"results %@", [results objectAtIndex:0]);

}

顺便说一句，NSLog结果输出如下：

results <NSManagedObject: 0x3d2d360> (entity: Entry; id: 0x3d13650 <x-coredata://6EA12ADA-8C0B-477F-801C-B44FE6E6C91C/Entry/p3> ; data: <fault>)

Answer 1

NSFetchRequest将返回与请求匹配的NSManagedObjects数组。这与你所看到的一致。假设您要获取名称，可以NSLog(@"the name is %@", [[results objectAtIndex:0] name]);打印出名称。

使用谓词获取数据。检索单个值

1 个答案: