改变self.navigationItem的显示标题

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self)
    {
        
        self.navigationItem.title = @"我收藏的优惠券";
        self.editButtonItem.possibleTitles = [NSSet setWithObjects:@"编辑", @"完成", nil];
        self.navigationItem.rightBarButtonItem = self.editButtonItem;
        self.editButtonItem.title = @"编辑";
        
    }
    return self;
}
//设置可以编辑；
-(void)setEditing:(BOOL)editing animated:(BOOL)animated
{
    
    [super setEditing:editing animated:animated];
    if (self.editing) {
        self.editButtonItem.title = @"完成";
    }
    else {
        self.editButtonItem.title = @"编辑";
    }
    [discountTableView setEditing:editing animated:animated];
    
}