过滤NSMutableArray的结果

NSMutableArray如下：

(
        {
        City = "Orlando";
       Name = "Shoreline Dental";
        State = Florida;
    },
        {
        City = "Alabaster ";
        Name = Oxford Multispeciality;
        State = Alabama;
    },
        {
        City = Dallas;
        Name = "Williams Spa";
        State = Texas;
    },
        {
        City = "Orlando ";
        Name = "Roast Street";
        State = Florida;
    }
)

怎么实现根据state"FLorida"对NSMutableArray进行分组:

(
        {
        City = "Orlando";
       Name = "Shoreline Dental";
        State = Florida;
    },
 {
        City = "Orlando ";
        Name = "Roast Street";
        State = Florida;
    }
)

代码还是现实先前的四个dictionary。

NSSortDescriptor *valueDescriptor = [[NSSortDescriptor alloc] initWithKey:@"Florida" ascending:YES];
       NSArray * descriptors = [NSArray arrayWithObject:valueDescriptor];
        NSArray * sortedArray = [arr sortedArrayUsingDescriptors:descriptors];