如何使用predicateWithFormat查询NSSet中包含的NSString [英] How can I use predicateWithFormat for query a NSString is contained in an NSSet

问题描述

使用StackMob作为后端。我有一个 Event 实体，该实体的关系称为用户 users （类型为 NSSet ）。现在，我想获取某些用户的用户名为 @ someuser 的所有事件。我的代码是这样的：

Using StackMob as backend. I have an Event entity which has a relationship called user users (type NSSet). Right now I want to get all the events that some user's username is @"someuser". My code like this:

[self.client getLoggedInUserOnSuccess:^(NSDictionary *result) {
        NSString *currentlyLoggedInUser = [result valueForKey:@"username"];

        NSFetchRequest *request = [[NSFetchRequest alloc] init];
        NSEntityDescription *eventEntity = [NSEntityDescription entityForName:@"Event" inManagedObjectContext:self.managedOjbectContext];
        [request setEntity:eventEntity];

        NSPredicate *predicate = [NSPredicate predicateWithFormat:@"ANY users.username = %@", currentlyLoggedInUser];
        NSLog(@"predicate: %@", predicate);
        [request setPredicate:predicate];
        NSLog(@"request: %@", request);
        events = [NSArray new];
        events = [self.managedOjbectContext executeFetchRequest:request error:nil];

        /* this is working...
        for (Event *e in events) {
            NSLog(@"%@",[e.users filteredSetUsingPredicate:[NSPredicate predicateWithFormat:@"username == %@", currentlyLoggedInUser]]);

        }
         */
        NSLog(@"events: %@", events);
    } onFailure:^(NSError *error) {

    }];

推荐答案

如果我正确理解了您的问题，则必须使用以下谓词：

If I understand your question correctly, you have to use the following predicate:

NSString *userName = @"some user";
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"ANY users.username = %@", userName];

它将查找具有任何具有给定用户名的用户的所有事件。

It finds all events that have any user with the given user name.

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