UINavigationController左侧返回按钮贴近左边的解决方案

解决UINavigationControll自定义返回按钮的时候图标贴近左边的解决方案，适配代码如下:

   UIBarButtonItem *leftButtonItem = [[UIBarButtonItem alloc] initWithCustomView:custonButton];   
   UIBarButtonItem *marginItem = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemFixedSpace target:nil action:nil];
   marginItem.width = -9;
   NSArray *array = [NSArray arrayWithObjects:marginItem,leftButtonItem, nil];
   self.navigationItem.leftBarButtonItems = array;