NSFetchedResultsController按名字或姓氏排序 [英] NSFetchedResultsController sort by first name or last name

问题描述

我基本上是在尝试实现

I am basically trying to achieve NSSortDescriptor with first name and last name,or with either first name or last name? but with an NSFetchedResultsController. I am reading records from the address book and want to display them just like the Address Book does.

将根据姓氏的首字母将记录分为几部分.如果没有姓氏，则按名字排序；如果没有名字，则按公司排序.

The records will be sorted into sections based on first letter of last name. If there isn't a last name it will sort by first name and if there isn't a first name it will sort by company.

目前我有

- (NSFetchedResultsController *)fetchedResultsController {

    if (_fetchedResultsController != nil) {
        return _fetchedResultsController;
    }

    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
    // read the contact list
    NSEntityDescription *entity = [Contact MR_entityDescriptionInContext:[NSManagedObjectContext MR_defaultContext]];
    [fetchRequest setEntity:entity];

    // sort the results by last name then by first name
    NSSortDescriptor *sort1 = [[NSSortDescriptor alloc] initWithKey:@"lastName" ascending:YES selector:@selector(caseInsensitiveCompare:)];
    NSSortDescriptor *sort2 = [[NSSortDescriptor alloc] initWithKey:@"firstName" ascending:YES selector:@selector(caseInsensitiveCompare:)];
    [fetchRequest setSortDescriptors:@[sort1, sort2]];

    // Fetch all the contacts and group them by the firstLetter in the last name. We defined this method in the CoreData/Human/Contact.h file
    NSFetchedResultsController *theFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:[NSManagedObjectContext MR_defaultContext] sectionNameKeyPath:@"firstLetter" cacheName:nil];

    self.fetchedResultsController = theFetchedResultsController;
    _fetchedResultsController.delegate = self;

    return _fetchedResultsController;

}

按姓氏，然后按名字排序.我该如何更改才能返回上面列出的所需结果?

Which sorts by last name and then first name. How would I alter this to return the wanted results listed above?

推荐答案

您可以在具有该逻辑的Contact上创建一个实例方法:

You can just create an instance method on Contact that has that logic:

- (NSString *)sortKey
{
    if(self.lastName) {
        return [self.lastName substringToIndex:1];
    }

    if(self.firstName) {
        return [self.firstName substringToIndex:1];
    }

    return [self.companyName substringToIndex:1];
}

然后只有一个使用键sortKey

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