相对于日期

Question

PLZ排序字典的指导我如何解决这字典

 
dict= 
{ 
"april 2012"=[1,2 ,3 ,4], 
"march 2013"=[3,4,6,7], 
"may 2013"=[6,7,8,3], 
"june 2013"=[6,6,7,8,3], 

} 

如何相对于日期从新到旧排序。

Answer 1

运行这段代码

NSMutableDictionary *dict = [NSMutableDictionary dictionary]; 
[dict setObject:@[@6,@6,@7,@8, @3] forKey:@"june 2013"]; 
[dict setObject:@[@1,@2,@3,@4] forKey:@"april 2012"]; 
[dict setObject:@[@6,@7,@8,@3] forKey:@"may 2013"]; 
[dict setObject:@[@3,@4,@6,@7] forKey:@"march 2013"]; 

NSDateFormatter *dateFormatter = [NSDateFormatter new]; 
dateFormatter.dateFormat = @"MMMM yyyy"; 
NSArray *keys = [dict allKeys]; 
NSArray *sortedKeys = [keys sortedArrayUsingComparator:^NSComparisonResult(id obj1, id obj2) { 
    NSDate *date1 = [dateFormatter dateFromString:obj1]; 
    NSDate *date2 = [dateFormatter dateFromString:obj2]; 

    return [date1 compare:date2]; 
}]; 

NSLog(@"%@", sortedKeys); 

我得到

2013-04-28 18:02:10.322 Test[746:19d03] (
    "april 2012", 
    "march 2013", 
    "may 2013", 
    "june 2013" 
) 

希望它能帮助。

编辑

为了得到相反的顺序排列替换随返回：

NSComparisonResult result = [date1 compare:date2]; 
    if (result == NSOrderedDescending) { 
     return NSOrderedAscending; 
    } else if (result == NSOrderedAscending) { 
     return NSOrderedDescending; 
    } else { 
     return NSOrderedSame; 
    } 

或者你也可以反转阵列（How can I reverse a NSArray in Objective-C?）的顺序，或只是在相反的顺序

迭代