Question

我有NSPredicate在NSArray个ID内搜索id，

之类的东西

('id in %@',array)

有没有办法让该获取的结果集按照相同的数组顺序排序？

我现在的代码是

+(NSArray*)     findIn:(NSArray*)identifiers{

    if(identifiers == nil) return nil;

    NSPredicate *searchFilter   = [NSPredicate predicateWithFormat:@"id IN %@", identifiers];
    NSArray     *fetchedObjects =  [GSBaseModel setupFetch:[[self class] managedObjectEntityName] andFilter:searchFilter andSortKey:nil];

    if([fetchedObjects count] == 0){
        return nil;
    }
    return fetchedObjects;
}

setupfecth只执行以下操作：

NSFetchRequest      *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity   = [NSEntityDescription entityForName:entityName inManagedObjectContext:[NSManagedObjectContext MR_defaultContext]];
[fetchRequest setEntity:entity];
return  = [[NSManagedObjectContext MR_defaultContext] executeFetchRequest:fetchRequest error:&error];

Answer 1

如果你想获取核心数据对象并用id数组链接它们，你应该考虑使用功能强大的NSDictionary：

因此，一旦获取了所有对象，只需将这些对象存储在由id：

键入的字典中

NSDictionary *managedObjectsKeyedByID = [NSDictionary dictionaryWithObjects:fetchedObjects forKeys:[fetchedObjects valueForKey:@"identifier"]];

现在，您可以遍历数组并使用字典检查匹配项：

for (NSString *identifier in arrayOfServerIDs) {
    NSManagedObject *existingObject = managedObjectsKeyedByID[identifier];
    if(!existingObject) {
       //insert a new one
    } else {
       //update
    }
}

Answer 2

我终于以这种方式推了它

感谢Sort NSArray of custom objects based on sorting of another NSArray of strings

+(NSArray*)sortWithArray:(NSArray*)toSort sorted:(NSArray*)sortedIdentifiers{
    NSMutableArray *sorted = [NSMutableArray array];

    // pre-populate with objects
    for (int i = 0; i < sortedIdentifiers.count; i++)
    {
        [sorted addObject:[NSNull null]];
    }
    // place the items at the correct position
    for (NSManagedObject *a in toSort)
    {
        NSNumber* identifier = [a valueForKey:@"id"];
        NSUInteger idx = [sortedIdentifiers indexOfObject:[identifier stringValue]];
        if (idx != NSNotFound)
        {
            [sorted setObject:a atIndexedSubscript:idx];
        }
    }
    // finally remove all the unecesarry placeholders if one array was smaller
    [sorted removeObject:[NSNull null]];
    return sorted;
}

使用带有数组顺序的in子句对NSPredicate进行排序

2 个答案: