Records about the use of RAC

// iterate content 
    NSArray Array * = @ [ @ " . 1 " , @ " 2 " , @ " . 3 " , @ " . 4 " , @ " . 5 " , @ " . 6 " ]; 
    [array.rac_sequence.signal subscribeNext: ^ ( ID   _Nullable X) { 
        NSLog ( @ " array contents:% @ " , X); 
    }]; 

    // brush option 
    NSArray * filter = [[array.rac_sequence filter :^BOOL(id value) {
        return  [value integerValue] > 2;
    }] array];
    NSLog(@"filter:%@",filter);   // (3,4,5,6)