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[英]Fetch NSarray from the NSDictionary of NSArray using objectForKey
[英]Return NSArray from NSDictionary
我有一個訪存,它返回一個包含字典的數組,其中包含核心數據對象的屬性。
這是我以前的問題: 從NSFetchResultsController的NSObject屬性創建數組
這是提取:
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];
當我記錄NSArray data
,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";
}
)
我想要的是具有這種格式的數組:
[NSArray arrayWithObjects: @"2011-11-01 00:00:00 +0000", @"2011-12-01 00:00:00 +0000", nil];'
編輯:
這是我要用新數據數組替換數據數組的方法:
- (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];
}
對從提取請求返回的數組對象調用valueForKey
。 這將依次調用每個對象的valueForKey
並返回所有結果值的數組。
NSArray *timestamps = [objects valueForKey:@"timeStamp"];
快速枚舉方法:
NSMutableArray *data = [[NSMutableArray alloc] initWithCapacity:array.count];
for (NSDictionary *d in objects) {
[data addObject:[d objectForKey:@"timeStamp"]];
}
塊枚舉器方法:
NSMutableArray *data = [[NSMutableArray alloc] initWithCapacity:array.count];
[objects enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
[data addObject:[obj objectForKey:@"timeStamp"]];
}];
無論哪種方式,“數據”都只包含NSDate實例的數組。
要獲得所需的數組類型,可以執行以下操作:
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];
希望這個能對您有所幫助!!
〜馬諾
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