按日期将对象数组排序到TableView中

Question

我用这个答案按日期对2个对象进行排序，效果非常好：获得一个NSArray

我现在需要按日期对3个对象进行排序，而无法完全修改我必须做的事情，才能做到这一点。

API/RSS提要中的所有文章将按日期在1 tableView中排序

以下是我尝试过的：

- (void)sortCombinedModel {
    // All 3
    [self.combinedModel sortUsingComparator:^NSComparisonResult(id a, id b, id c) {
        NSDate *dateA, *dateB, *dateC;
        dateA = ([a isKindOfClass:[FeedRSS self]])? ((FeedRSS *)a).pubDate : ((Data *)a).created_time : ((YaRSS *)a).pubDate;
        dateB = ([b isKindOfClass:[FeedRSS self]])? ((FeedRSS *)b).pubDate : ((Data *)b).created_time : ((YaRSS *)b).pubDate;
        dateC = ([c isKindOfClass:[FeedRSS self]])? ((FeedRSS *)c).pubDate : ((Data *)c).created_time : ((YaRSS *)c).pubDate;
        return [dateB compare:dateA compare:dateC];
    }];   
}

你能帮我把3个日期排序吗

---

如果需要，请提供其他信息：

我发现了如何修改这个部分-有3个API/RSS提要进入一个NSMutableArray:

- (void)loadMedia {
    self.combinedModel = [NSMutableArray array];
    // Here's the #1
    [self loadOneWithSuccess:^(RKObjectRequestOperation *operation, RKMappingResult *mappingResult) {
        [self.combinedModel addObjectsFromArray:mappingResult.array];
    // Here's the trick.  call API2 here.  Doing so will serialize these two requests
    [self loadTwoWithSuccess:^(RKObjectRequestOperation *operation, RKMappingResult *mappingResult) {
        [self.combinedModel addObjectsFromArray:mappingResult.array];
    // Here's the trick.  call API3 here.  Doing so will serialize these two requests
    [self loadThreeWithSuccess:^(RKObjectRequestOperation *operation, RKMappingResult *mappingResult) {
        [self.combinedModel addObjectsFromArray:mappingResult.array];
        [self sortCombinedModel];
        [self.tableView reloadData];
    } failure:^(RKObjectRequestOperation *operation, NSError *error) {
        NSLog(@"No?: %@", error);
    }];
    } failure:^(RKObjectRequestOperation *operation, NSError *error) {
            NSLog(@"No?: %@", error);
    }];
    } failure:^(RKObjectRequestOperation *operation, NSError *error) {
        NSLog(@"No?: %@", error);
    }];
}

以下是以前排序2个日期的情况：

- (void)sortCombinedModel {
    [self.combinedModel sortUsingComparator:^NSComparisonResult(id a, id b) {
        NSDate *dateA, *dateB;
        dateA = ([a isKindOfClass:[Feed self]])? ((Feed *)a).published : ((Data *)a).created_time;
        dateB = ([b isKindOfClass:[Feed self]])? ((Feed *)b).published : ((Data *)b).created_time;
        return [dateA compare:dateB];
    }];
}

Answer 1

比较器必须始终取两个值进行比较，但它希望检查这两个值是否为三种类型之一。将以下内容添加到FeedRSS.h、Data.h和YaRSS.h中定义的公共接口：

- (NSDate *)sortDate;

在每个实现中，添加一个返回正确日期属性的方法来对类进行排序，例如

// FeedRSS.m
- (NSDate *)sortDate {
    return self.pubDate;
}

Data.m（return self.created_time）和YaRSS.h的想法相同，返回对象要排序的任何日期

- (void)sortCombinedModel {
    [self.combinedModel sortUsingComparator:^NSComparisonResult(id a, id b) {
        NSDate *dateA = nil, *dateB = nil;
        if ([a isKindOfClass:[Feed self]]) { dateA = ((Feed *)a).sortDate; }
        else if ([a isKindOfClass:[Data self]]) { dateA = ((Data *)a).sortDate; }
        else if ([a isKindOfClass:[YaRSS self]]) { dateA = ((YaRSS *)a).sortDate; }
        if ([b isKindOfClass:[Feed self]]) { dateB = ((Feed *)b).sortDate; }
        else if ([b isKindOfClass:[Data self]]) { dateB = ((Data *)b).sortDate; }
        else if ([b isKindOfClass:[YaRSS self]]) { dateB = ((YaRSS *)b).sortDate; }
        return [dateA compare:dateB];
    }];
}

如果数组只包含所需的三种对象，则此操作有效。如果你总是想这样排序，一个更整洁的方法是实现compare：在这些类中的每一个中，在每个类中检查param是否是其他两种类型中的一种。