我有一个DiaryEntry对象的NSArray，其中每个DiaryEntry都有一个NSDate date_字段。
我想在表格视图中显示所有DiaryEntry，按星期几分组，
其中每个组按日期升序排列。
因此，我需要使用NSArray，并转换为NSDictionary数组，其中键是星期几（NSDate），值是DiaryEntrys的NSArray，由date_字段按升序排序。
我认为这是一个非常常见的操作，但是在任何地方都找不到任何示例代码。
任何帮助是极大的赞赏。
谢谢！！
最佳答案
以下应该工作（没有实际编译和测试代码）
NSEnumerator* enumerator;
DiaryEntrys* currEntry;
NSMutableDictionary* result;
/*
use sorting code from other answer, if you don't sort, the result will still contain arrays for each day of the week but arrays will not be sorted
*/
[myArray sortUsingDescriptors:....];
/*
result holds the desired dictionary of arrays
*/
result=[[NSMutableDictionary alloc] init];
/*
iterate throught all entries
*/
enumerator=[myArray objectEnumerator];
while (currEntry=[enumerator nextObject])
{
NSNumber* currDayOfTheWeekKey;
NSMutableArray* dayOfTheWeekArray;
/*
convert current entry's day of the week into something that can be used as a key in an dictionary
I'm converting into an NSNumber, you can choose to convert to a maningfull string (sunday, monday etc.) if you like
I'm assuming date_ is an NSCalendarDate, if not, then you need a method to figure out the day of the week for the partictular date class you're using
Note that you should not use NSDate as a key because NSDate indicates a particular date (1/26/2010) and not an abstract "monday"
*/
currDayOfTheWeekKey=[NSNumber numberWithInt:[[currEntry valueForKey:@"date_"] dayOfWeek]];
/*
grab the array for day of the week using the key, if exists
*/
dayOfTheWeekArray=[result objectForKey:currDayOfTheWeekKey];
/*
if we got nil then this is the first time we encounter a date of this day of the week so
we create the array now
*/
if (dayOfTheWeekArray==nil)
{
dayOfTheWeekArray=[[NSMutableArray alloc] init];
[result setObject:dayOfTheWeekArray forKey:currDayOfTheWeekKey];
[dayOfTheWeekArray release]; // retained by the dictionary
}
/*
once we figured out which day the week array to use, add our entry to it.
*/
[dayOfTheWeekArray addObject:currEntry];
}