Iphone 从NSDictionary返回NSArray

我有一个fetch，它返回一个数组，其中包含核心数据对象属性的字典

这是我先前的问题：

这是提取：

NSFetchRequest *request = [[NSFetchRequest alloc] init];
[request setEntity:entity];
[request setResultType:NSDictionaryResultType];
[request setReturnsDistinctResults:NO]; //set to YES if you only want unique values of the property
[request setPropertiesToFetch :[NSArray arrayWithObject:@"timeStamp"]]; //name(s) of properties you want to fetch

// Execute the fetch.
NSError *error;
NSArray *objects = [managedObjectContext executeFetchRequest:request error:&error];

当我记录NSArray

数据时，我得到以下信息：

The content of data is(
        {
        timeStamp = "2011-06-14 21:30:03 +0000";
    },
        {
        timeStamp = "2011-06-16 21:00:18 +0000";
    },
        {
        timeStamp = "2011-06-11 21:00:18 +0000";
    },
        {
        timeStamp = "2011-06-23 19:53:35 +0000";
    },
        {
        timeStamp = "2011-06-21 19:53:35 +0000";
    }
)

我想要的是一个具有以下格式的数组：

[NSArray arrayWithObjects: @"2011-11-01 00:00:00 +0000", @"2011-12-01 00:00:00 +0000", nil];'

编辑：

这是我想用新数据数组替换数据数组的方法：

- (NSArray*)calendarMonthView:(TKCalendarMonthView *)monthView marksFromDate:(NSDate *)startDate toDate:(NSDate *)lastDate {    
    NSLog(@"calendarMonthView marksFromDate toDate");   
    NSLog(@"Make sure to update 'data' variable to pull from CoreData, website, User Defaults, or some other source.");
    // When testing initially you will have to update the dates in this array so they are visible at the
    // time frame you are testing the code.
    NSArray *data = [NSArray arrayWithObjects:
                     @"2011-01-01 00:00:00 +0000", @"2011-12-01 00:00:00 +0000", nil]; 


    // Initialise empty marks array, this will be populated with TRUE/FALSE in order for each day a marker should be placed on.
    NSMutableArray *marks = [NSMutableArray array];

    // Initialise calendar to current type and set the timezone to never have daylight saving
    NSCalendar *cal = [NSCalendar currentCalendar];
    [cal setTimeZone:[NSTimeZone timeZoneForSecondsFromGMT:0]];

    // Construct DateComponents based on startDate so the iterating date can be created.
    // Its massively important to do this assigning via the NSCalendar and NSDateComponents because of daylight saving has been removed 
    // with the timezone that was set above. If you just used "startDate" directly (ie, NSDate *date = startDate;) as the first 
    // iterating date then times would go up and down based on daylight savings.
    NSDateComponents *comp = [cal components:(NSMonthCalendarUnit | NSMinuteCalendarUnit | NSYearCalendarUnit | 
                                                    NSDayCalendarUnit | NSWeekdayCalendarUnit | NSHourCalendarUnit | NSSecondCalendarUnit) 
                                          fromDate:startDate];
    NSDate *d = [cal dateFromComponents:comp];

    // Init offset components to increment days in the loop by one each time
    NSDateComponents *offsetComponents = [[NSDateComponents alloc] init];
    [offsetComponents setDay:1];    


    // for each date between start date and end date check if they exist in the data array
    while (YES) {
        // Is the date beyond the last date? If so, exit the loop.
        // NSOrderedDescending = the left value is greater than the right
        if ([d compare:lastDate] == NSOrderedDescending) {
            break;
        }

        // If the date is in the data array, add it to the marks array, else don't
        if ([data containsObject:[d description]]) {
            [marks addObject:[NSNumber numberWithBool:YES]];
        } else {
            [marks addObject:[NSNumber numberWithBool:NO]];
        }

        // Increment day using offset components (ie, 1 day in this instance)
        d = [cal dateByAddingComponents:offsetComponents toDate:d options:0];
    }

    [offsetComponents release];

    return [NSArray arrayWithArray:marks];
}

快速枚举法：

NSMutableArray *data = [[NSMutableArray alloc] initWithCapacity:array.count];
for (NSDictionary *d in objects) {
  [data addObject:[d objectForKey:@"timeStamp"]];
}

方法：

无论哪种方式，“data”都只包含一个NSDate实例数组。
调用从fetch请求返回的数组对象。这将依次调用每个对象上的
valueForKey
，并返回所有结果值的数组

NSArray *timestamps = [objects valueForKey:@"timeStamp"];

要获得所需的数组类型，可以执行以下操作：

NSMutableArray *array = [[NSMutableArray alloc] init];
for (int n = 0; n < [data count]; n++) // data array 
 {  
    NSMutableArray *array = [[NSMutableArray alloc] init];
    array = [NSMutableArray arrayWithObjects:[[data objectAtIndex:n] valueForKey:@"timeStamp"] ,nil];
   if ([array count] != 0) {
    [newArray addObject:[array objectAtIndex:0]];
    }
  }
 [array release];

NSMutableArray*array=[[NSMutableArray alloc]init]；
对于（int n=0；n<[数据计数]；n++）//数据数组
{  
NSMUTABLEARRY*array=[[NSMUTABLEARRY alloc]init]；
数组=[NSMutableArray arrayWithObjects:[[data objectAtIndex:n]valueForKey:@“timeStamp”]，nil]；
如果（[数组计数]！=0）{
[newArray addObject:[array objectAtIndex:0]]；
}
}
[阵列释放]；

希望这对你有帮助

~Manoj
太棒了。我喜欢KVC，每天都能学到一些新的东西。谢谢Anurag。但是由于某些原因，数据仍然没有加载我的日历视图。这是一张显示2个阵列的图片，底部的一个加载数据很好，并与示例应用程序一起提供。最上面的是我的，不加载数据。是不是因为我的时间戳必须是000000？实际上，我刚刚发布了上面的方法，这个数组就是其中的一部分。也许有些东西我可以改变，所以时间0000000与时间戳中的时间没有什么区别？@ RYANR -KVC给可可提供了一个非常坚实的基础。我喜欢其他一些语言使用
map
、
reduce、
过滤器处理集合的方式。例如，在Ruby中，等价物是，
timestamps=objects.map{{| object | object[：timestamp]}
。希望Cocoa能将这些方法合并到NSArray中，也许其他语言也会采用KVC。一厢情愿：）@Anurag：到目前为止，除了你刚才演示的，我最喜欢的是。在一行代码中对一个集合执行函数简直太棒了。你能检查一下我发布的另一个答案中的注释，看看你知道发生了什么吗？谢谢。@Jon，我不知道你的意思，我在你的另一个问题或这个问题的其他地方没有看到任何新的评论。你能澄清一下吗？根据Anurag提供的答案，我们正在讨论一个我们无法解决的问题。
NSMutableArray *array = [[NSMutableArray alloc] init];
for (int n = 0; n < [data count]; n++) // data array 
 {  
    NSMutableArray *array = [[NSMutableArray alloc] init];
    array = [NSMutableArray arrayWithObjects:[[data objectAtIndex:n] valueForKey:@"timeStamp"] ,nil];
   if ([array count] != 0) {
    [newArray addObject:[array objectAtIndex:0]];
    }
  }
 [array release];