按月将带有NSDate对象的NSArray排序为NSDictionary [英] Sort NSArray with NSDate object into NSDictionary by month

问题描述

我正在构建 UITableView ，并希望按月分组，以便我可以将这些字符串作为我的节标题，例如：

I am building a UITableView and would like to group by month so that I can have those strings as my section headers, e.g.:

February 2013
- Item 1
- Item 2

January 2013
- Item 1
- Item 2

我有 NSArray 具有自定义对象，这些对象的pubDate属性为 NSDate 。

I have an NSArray which has custom objects that have a pubDate property that is an NSDate.

如何使用 NSDate 对象将我的自定义对象按月分组为 NSDictionary ？

How can I use that NSDate object to group my custom objects into a NSDictionary by month?

推荐答案

像这样排序数组

NSArray *sortedArray = [yourArrayOfCustomObjects sortedArrayUsingComparator:^NSComparisonResult(id obj1, id obj2) {
        NSDate *firstDate = [(YourCustomObject*)obj1 pubDate];
        NSDate *secondDate = [(YourCustomObject*)obj2 pubDate];
        return [firstDate compare:secondDate];        

    }];

//现在简单迭代即可确定所有相同月份的条目。

// Now a simple iteration and you can determine all same month entries.

//代码不是仅出于说明目的而已。

// Code is not complete just for illustration purpose.

//您还必须处理Year更改。

// You have to handle Year change as well.

int curMonth = 0;
int prevMonth = 0;
foreach(CustomObject *obj in sortedArray)
{
   NSDateComponents *components = [[NSCalendar currentCalendar] components:NSDayCalendarUnit | NSMonthCalendarUnit | NSYearCalendarUnit fromDate:obj.pubDate];
   prevMonth = curMonth; 
   curMonth = components.month;
   if(prevMonth != 0 && curMonth != prevMonth)
   {
      //Month Changed
   }
}

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