我有一个带有整数值的NSMutableDictionary
,我想得到一个按键数组,按各自的值递增排序。例如,使用此词典:
mutableDict = {
"A" = 2,
"B" = 4,
"C" = 3,
"D" = 1,
}
我想结束数组["D", "A", "C", "B"]
。当然,我真正的字典比四个项目大得多。
答案 0 :(得分:66)
NSDictionary
方法keysSortedByValueUsingComparator:
应该可以解决问题。
您只需要一个返回NSComparisonResult
的方法来比较对象的值。
你的词典是
NSMutableDictionary * myDict;
你的数组是
NSArray *myArray;
myArray = [myDict keysSortedByValueUsingComparator: ^(id obj1, id obj2) {
if ([obj1 integerValue] > [obj2 integerValue]) {
return (NSComparisonResult)NSOrderedDescending;
}
if ([obj1 integerValue] < [obj2 integerValue]) {
return (NSComparisonResult)NSOrderedAscending;
}
return (NSComparisonResult)NSOrderedSame;
}];
只需使用NSNumber
个对象而不是数字常量。
答案 1 :(得分:27)
NSDictionary有一个名为allKeys
的简洁方法。
如果您希望对数组进行排序,keysSortedByValueUsingComparator:
应该可以解决问题。
理查德的解决方案也有效,但会做一些你不一定需要的额外电话:
// Assuming myDictionary was previously populated with NSNumber values.
NSArray *orderedKeys = [myDictionary keysSortedByValueUsingComparator:^NSComparisonResult(id obj1, id obj2){
return [obj1 compare:obj2];
}];
答案 2 :(得分:14)
这是一个解决方案:
NSDictionary *dictionary; // initialize dictionary
NSArray *sorted = [[dictionary allKeys] sortedArrayUsingComparator:^NSComparisonResult(id obj1, id obj2) {
return [[dictionary objectForKey:obj1] compare:[dictionary objectForKey:obj2]];
}];
答案 3 :(得分:14)
最简单的解决方案:
[dictionary keysSortedByValueUsingSelector:@selector(compare:)]
答案 4 :(得分:2)
我在这里做了类似的事情:
NSMutableArray * weekDays = [[NSMutableArray alloc] initWithObjects:@"Sunday",@"Monday",@"Tuesday",@"Wednesday",@"Thursday",@"Friday",@"Saturday", nil];
NSMutableDictionary *dict = [[NSMutableDictionary alloc] init];
NSMutableArray *dictArray = [[NSMutableArray alloc] init];
for(int i = 0; i < [weekDays count]; i++)
{
dict = [NSMutableDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithInt:i],@"WeekDay",[weekDays objectAtIndex:i],@"Name",nil];
[dictArray addObject:dict];
}
NSLog(@"Before Sorting : %@",dictArray);
@try
{
//for using NSSortDescriptor
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"WeekDay" ascending:YES];
NSArray *descriptor = @[sortDescriptor];
NSArray *sortedArray = [dictArray sortedArrayUsingDescriptors:descriptor];
NSLog(@"After Sorting : %@",sortedArray);
//for using predicate
//here i want to sort the value against weekday but only for WeekDay<=5
int count=5;
NSPredicate *Predicate = [NSPredicate predicateWithFormat:@"WeekDay <=%d",count];
NSArray *results = [dictArray filteredArrayUsingPredicate:Predicate];
NSLog(@"After Sorting using predicate : %@",results);
}
@catch (NSException *exception)
{
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Sorting cant be done because of some error" message:[NSString stringWithFormat:@"%@",exception] delegate:self cancelButtonTitle:@"Ok" otherButtonTitles:nil];
[alert setTag:500];
[alert show];
[alert release];
}