將包有 dictionary 的 nsarray 轉成 dictionary ， key 為高亮的那一行。

- (NSMutableDictionary *)indexKeyedDictionaryFromArray:(NSArray *)array
{
    id objectInstance;
    
    NSMutableDictionary *mutableDictionary = [[NSMutableDictionary alloc] init];
    for (objectInstance in array) {
        
        [mutableDictionary setObject:objectInstance forKey:[NSString stringWithFormat:@"%@", [objectInstance objectForKey:@"name"]]];

    }
    return (NSMutableDictionary *)mutableDictionary;
}

使用範例

    NSArray *array = [NSArray arrayWithObjects:
                      [NSDictionary dictionaryWithObjectsAndKeys:@"mark", @"name", @"100", @"score", nil],
                      [NSDictionary dictionaryWithObjectsAndKeys:@"tom", @"name", @"78", @"score", nil],
                      [NSDictionary dictionaryWithObjectsAndKeys:@"mary", @"name", @"81", @"score", nil],
                      [NSDictionary dictionaryWithObjectsAndKeys:@"sandy", @"name", @"65", @"score", nil],
                      [NSDictionary dictionaryWithObjectsAndKeys:@"sam", @"name", @"98", @"score", nil],
                      nil];
    
    NSDictionary *dictionary = [self indexKeyedDictionaryFromArray:array];

這也是新手滿常見的問題， nsdictionary 裡有 name 跟 score 的值，產生一個由低分到高分的 keys 陣列。
這個方法可以自訂一些條件，nsmutabledictionary也同樣適用喔。

NSMutableDictionary *dict = [NSDictionary dictionaryWithObjectsAndKeys:
                          
                          [NSDictionary dictionaryWithObjectsAndKeys:@"mark", @"name", @"100", @"score", nil], @"mark",
                          [NSDictionary dictionaryWithObjectsAndKeys:@"tom", @"name", @"78", @"score", nil], @"tom",
                          [NSDictionary dictionaryWithObjectsAndKeys:@"mary", @"name", @"81", @"score", nil], @"mary",
                          [NSDictionary dictionaryWithObjectsAndKeys:@"sandy", @"name", @"65", @"score", nil], @"sandy",
                          [NSDictionary dictionaryWithObjectsAndKeys:@"sam", @"name", @"98", @"score", nil], @"sam",
                          
                          nil];

NSArray *blockSortedKeys = [dict keysSortedByValueUsingComparator: ^(id obj1, id obj2) {
        
        if ([[obj1 objectForKey:@"score"] intValue] > [[obj2 objectForKey:@"score"] intValue]) {
            
            return (NSComparisonResult)NSOrderedDescending;
        }
        
        if ([[obj1 objectForKey:@"score"] intValue] < [[obj2 objectForKey:@"score"] intValue]) {
            
            return (NSComparisonResult)NSOrderedAscending;
        }
        
        return (NSComparisonResult)NSOrderedSame;

    }];