從可變詞典中提取特定數據

Question

我有一個可變詞典，它允許人們選擇星期幾。一旦選擇了一天，狀態就會使用numberWithBool進行更新。

當我的NSLog它看起來像這樣的輸出：

{ 
    day = Monday; 
    isSelected = 1; 
}, 
    { 
    day = Tuesday; 
    isSelected = 0; 
}, 
    { 
    day = Wednesday; 
    isSelected = 0; 
}, 
    { 
    day = Thursday; 
    isSelected = 0; 
}, 
    { 
    day = Friday; 
    isSelected = 0; 
}, 
    { 
    day = Saturday; 
    isSelected = 0; 
}, 
    { 
    day = Sunday; 
    isSelected = 1; 
} 

我希望能夠提取所選擇的天，產生一個字符串的形式輸出。所以在這個例子中，輸出將是：週一，週日

我該怎麼做？

我創建的字典代碼如下：

NSMutableArray * tempSource = [[NSMutableArray alloc] init]; 
NSArray *daysOfWeek = [NSArray arrayWithObjects:@"Monday", @"Tuesday", @"Wednesday", @"Thursday", @"Friday", @"Saturday", @"Sunday",nil]; 
for (int i = 0; i < 7; i++) 
{ 
    NSString *dayOfWeek = [daysOfWeek objectAtIndex:i]; 
    NSMutableDictionary *dict = [NSMutableDictionary dictionaryWithObjectsAndKeys:dayOfWeek, @"day", [NSNumber numberWithBool:NO], @"isSelected",nil]; 
    [tempSource addObject:dict]; 
} 

[self setSourceArray:tempSource]; 
[tempSource release]; 

Answer 1

您可以循環通陣列中所有的項目，並建立一個側陣列只含當天（1）名稱，或者您也可以使用謂詞，然後使用KVC直接提取日期（2）。

然後將過濾數組的組件加入到字符串中。

解決方案1：

NSMutableArray selectedDays = [[NSMutableArray alloc] init]; 
for(NSDictionary* entry in sourceArray) 
{ 
    if (([entry objectForKey:@"isSelected"] boolValue]) { 
     [selectedDays addObject:[entry objectForKey:@"day"]]; 
    } 
} 
NSString days = [selectedDays componentsJoinedByString:@", "]; 
[selectedDays release]; 

解決方案2：

NSPredicate* filter = [NSPredicate predicateWithFormat:@"SELF.isSelected == 1"]; // not sure about the exact format (no mac here to test right now so you may adapt a bit if it does not work directly) 
// get the array of dictionaries but only the ones that have isSelected==1 
NSArray selectedEntries = [sourceArray filteredArrayUsingPredicate:filter]; 
NSArray selectedDays = [selectedEntries valueForKey:@"day"]; // extract the "days" keys of the dictionaries. We have a NSArray of strings then. 
NSString days = [selectedDays componentsJoinedByString:@", "]; 

---

作爲一個側面說明，你這樣做的方式是很奇怪的。爲什麼有NSArray的NSDictionaries呢？由於這是簡單的，而且只包含BOOL的靜態大小的數組，所以您可以改爲使用C數組BOOL selected[7]，而不是其他的。

然後有平日的名字，你應該使用的方法NSCalendar/NSDateFormatter/NSDateComponents（用正確的語言的用戶/區域設置自動），以獲得平日的標準名稱：使用創建一個NSDate一個NSDateComponent，您只需定義weekday組件，然後使用NSDateFormatter將其轉換爲字符串，然後選擇僅顯示星期幾名稱的字符串格式。

---

-(void)tableView:(UITableView*)tv didSelectRowAtIndexPath:(NSIndexPath*)indexPath { 
    // selectedDays is an instance variable in .h declared as 
    // BOOL selectedDays[7]; 
    selectedDays[indexPath.row] = ! selectedDays[indexPath.row]; 
    [tv reloadData]; 
} 

-(UITableViewCell*)tableView:(UITableView*)tv cellForRowAtIndexPath:(NSIndexPath*)indexPath { 
    static NSString* kCellIdentifier = @"DayCell"; 
    UITableViewCell* cell = [tv dequeueReusableCellWithIdentifier:kCellIdentifier]; 
    if (!cell) { 
    cell = [[[UITableViewCell alloc] initWithStyle:... identifier:kCellIdentifier]; autorelease]; 
    // configure here every property that is common to all for your cells (text color, etc) 
    } 

    // configure here things that will change from cell to cell 
    cell.accessoryType = selectedDays[indexPath.row] ? UITableViewCellAccessoryTypeCheckmarck : UITableViewCellAccessoryTypeNone; 
    cell.textLabel.text = weekdayName(indexPath.row); 

    return cell; 
} 

// Simple C function to return the name of a given weekday 
NSString* weekdayName(int weekday) 
{ 
#if WAY_1 
    /**** Solution 1 ****/ 
    // Optimization note: You may compute this once for all instead of recomputing it each time 
    NSDateComponents* comp = [[[NSDateComponents alloc] init] autorelease]; 
    [comp setWeekday:weekday+1]; // weekdays start at 1 for NSDateComponents 
    NSDate* d = [[NSCalendar currentCalendar] dateFromComponents:comp]; 

    NSDateFormatter* df = [[[NSDateFormatter alloc] init] autorelease]; 
    [df setDateFormat:@"EEEE"]; // format for the weekday 
    return [[df stringFromDate:d] capitalizedString]; 
#else 
    /**** Solution 2 ****/ 
    NSDateFormatter* df = [[[NSDateFormatter alloc] init] autorelease]; 
    NSArray* weekdayNames = [df weekdaySymbols]; // or maybe one of its sibling methods? check what is returned here to be sure 
    return [weekdayNames objectAtIndex:weekday]; 
#endif 
} 

Answer 2

是否有您避免NSMutableIndexSet理由嗎？

它可以簡化您的代碼：

NSArray *daysOfWeek = ...; 
NSMutableIndexSet *indexesOfSelectedDays = ...; 
NSArray *selectedDays = [daysOfWeek objectsAtIndexes:indexesOfSelectedDays]; 

Answer 3

使用NSPredicate創建選擇數組，其中isSelected是真實的項目謂詞，並用它來使用NSArray的-filteredArrayUsingPredicate:方法濾鏡陣列。 （@Miraaj發佈使用謂詞的速度比我可以輸入它的一個很好的例子。）然後採取濾波陣列，並挑選出的日子裏，像這樣的：

NSArray *selectedItems = [sourceArray filteredArrayUsingPredicate:somePredicate]; 
NSArray *days = [selectedItems valueForKey:@"day"]; 
NSString *daysString = [days componentsJoinedByString@", "];