对数组里面的对象排序

views是一个nsarry类型，里面都是uiview，我们用uiview的tag来排序

    NSSortDescriptor *sortDescriptor;

    sortDescriptor = [[[NSSortDescriptor alloc] initWithKey:@"tag" ascending:YES] autorelease];

    NSArray *sortDescriptors = [NSArray arrayWithObject:sortDescriptor];

    
    [views sortUsingDescriptors:sortDescriptors];