为什么我的表格视图仅按升序显示日期，而不显示其余数据

debugcn 发表于 Dev

用户名

嗨，我制作了一个RSS feed应用程序，该应用程序从多个网站收集了feed项目并将它们发布在UITableView上，我尝试按日期升序对结果进行排序，目前唯一要排序的是数据，其余的则是我的数据（例如“名称”和“说明”）被混淆成随机的顺序，并且与日期不符。

(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{

CustomCell *cell = [tableView dequeueReusableCellWithIdentifier:@"Cell" forIndexPath:indexPath];


NSSortDescriptor *dateDescriptor = [NSSortDescriptor
                                    sortDescriptorWithKey:@"pubDate"
                                    ascending:YES];

NSDateFormatter *dateFormatter = [[NSDateFormatter alloc]init];
[dateFormatter setDateFormat:@"EEEE, dd MMM yyyy HH:mm:ss Z"];
NSString *date = [[feeds objectAtIndex:indexPath.row] objectForKey:@"pubDate"];
NSDate *finalDate = [dateFormatter dateFromString:date];
NSLog(@"displayDate = %@", finalDate);



NSArray *sortDescriptors = [NSArray arrayWithObject:dateDescriptor];
NSArray *sortedEventArray = [feeds
                             sortedArrayUsingDescriptors:sortDescriptors];




cell.customName.text = [[sortedEventArray objectAtIndex:indexPath.row] objectForKey: @"author"];


cell.customDescription.text = [[sortedEventArray objectAtIndex:indexPath.row] objectForKey: @"description"];

cell.customDate.text = [NSString stringWithFormat:@"%@", finalDate];

(void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName attributes:(NSDictionary *)attributeDict {

element = elementName;

if ([element isEqualToString:@"item"]) {


    item    = [[NSMutableDictionary alloc] init];
    author   = [[NSMutableString alloc] init];
    description    = [[NSMutableString alloc] init];
    pubDate    = [[NSMutableString alloc] init];
    link   = [[NSMutableString alloc] init];



}

}

(void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string {

if ([element isEqualToString:@"author"]) {
    [author appendString:string];
} else if ([element isEqualToString:@"link"])
{
    [link appendString:string];
} else if ([element isEqualToString:@"description"])
{
    [description appendString:string];
}
else if ([element isEqualToString:@"pubDate"])
{
    [pubDate appendString:string];
}



}

(void)parserDidEndDocument:(NSXMLParser *)parser {

     [self.tableView reloadData];

}

(void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName {

if ([elementName isEqualToString:@"item"]) {

    link = [NSMutableString stringWithString:
    [link stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]]];
    pubDate = [NSMutableString stringWithString:[pubDate stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]]];


    [item setObject:author forKey:@"author"];
    [item setObject:link forKey:@"link"];
    [item setObject:description forKey:@"description"];
    [item setObject:pubDate forKey:@"pubDate"];


    [feeds addObject:[item copy]];

}

}

姓名

不应在所有cellForRowAtIndexPath上进行排序。当表滚动时，将反复调用该方法。相反，请在完成时将xml项目插入正确排序的位置。

- (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName {

    // your existing code
    NSComparator comparator = ^(NSDictionary *a, NSDictionary *b) {
        return [a[@"pubDate"] compare:b[@"pubDate"]];
    };
    NSUinteger index = [feeds indexOfObject:item
                              inSortedRange:NSMakeRange(0, [feeds count])
                                    options:NSBinarySearchingInsertionIndex
                            usingComparator:comparator];

    [feeds insertObject:[item copy] atIndex:index];
}

不要feeds在cellForRowAtIndexPath中进行任何排序或操作。刚拿到物品。。。

NSDictionary *myModel = feeds[indexPath.row];
// and use it
cell.customName.text = myModel[@"author"];

更少的代码，更少的计算。

编辑

您的日期解释代码很棒，但是放错了位置。通过在cellForRowAtIndexPath：中完成它，然后将其丢弃，然后重做，依此类推。而且，它做得太晚了，无法在需要的地方进行排序。

取而代之的是，NSDate在解析过程中获取一个构建，并保留它。它是排序所需的，对于其他日期计算，您可能需要在应用程序中的其他位置进行。

// first, abstract your (perfectly good) date parse to it's own function
- (NSDate *)dateFromXml:(NSString *)dateString {

    // with static declaration, we'll create the date formatter only once
    // better than creating a formatter for every date we parse
    static NSDateFormatter *df;
    if (!df) {
        df = [[NSDateFormatter alloc]init];
        [df setDateFormat:@"EEEE, dd MMM yyyy HH:mm:ss Z"];
    }
    return [df dateFromString: dateString];
}

现在，让我们将NSDate表示形式添加到已解析的xml中。从现在开始，pubDate仅用于显示，我们将添加另一个名为pubDateObj的键来执行任何日期计算，例如排序：

- (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName {

    // your existing code
    // now add the new pubDateObj to the parse
    item[@"pubDateObj"] = [self dateFromXml:item[@"pubDate"]];

    // the sort code I suggest above, except:    
    NSComparator comparator = ^(NSDictionary *a, NSDictionary *b) {
        return [a[@"pubDateObj"] compare:b[@"pubDateObj"]];
    };
    // and so on as before
}

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