具有私有成员的类是具有基类指针的模板?

所以我不确定你的最终目标是什么，但让我快速猜测一下你可能想做什么：

所以你提到你有 2 个BaseBallPlayer子类，假设它们是MajorLeaguePlayer的，并且MinorLeagePlayer这个私有数组列表teamArrayList可用于保存基类的任何组合(BaseBallPlayer- 在您的情况下是MajorLeaguePlayer和MinorLeaguePlayer)。

您通常希望将此 teamArrayList 保留为私有状态，以便仅由您的公共方法安全地修改它。 因此，例如，您可能希望有一个PlayerDatabase的构造函数，该构造函数的参数为ArrayList<BaseBallPlayer *>

PlayerDatabase(ArrayList<BaseBallPlayer *> players) {
// set the private teamArray list in the constructor
teamArrayList = players;
}

或者，您可能希望根据基类BaseBallPlayer中的一个属性对 teamArray 列表进行排序

// or another one sorting for weight or name
void sortPlayerListByHeight() {
// sort the private team array list
teamArrayList = ... // sort by height
}

也许您想获取列表中的玩家数量，或者找到列表中的第一个或最后一个玩家。 一般来说，使用公共方法来访问/修改私有数据成员(即 teamArrayList)是一种很好的做法。

int numberOfPlayersInList() {
return teamArrayList.LengthIs();
}
BaseBallPlayer getFirstPlayerInList() {
return teamArrayList.RetrieveItem.... // get the first item in the list
}

然后从另一个类中，您可以构造一些子类对象并构造玩家数据库：

ArrayList<BaseBallPlayer *> playerList = new ArrayList<>();
playerList.add(new MinorLeagePlayer("minorName", 180,70);
playerList.add(new MajorLeaguePlayer("majorName", 200, 72);
PlayerDatabase db = new PlayerDatabase(playerList);
// now you can do some operations on the PlayerDatabase knowing that the list will contain all objects that can use methods from the Base Class (`BaseBallPlayer`)
db.getFirstPlayerInList().print_player(); // method from your base class implemented in your subclasses

int numberOfPlayers = db.numberOfPlayersInList();
// do something with the number of players in the list

这是伪代码，但希望它能帮助您了解这个想法。

编辑与我们的评论相关：

ArrayList<BaseBallPlayer *> *playerList = new ArrayList<BaseBallPlayer *>();
MinorLeaguePlayer *aPlayer = new MinorLeaguePlayer();
playerList->InsertItem(aPlayer);

我在 ArrayList 构造函数、MinorLeaguePlayer 构造函数和 InsertItem 方法中包含了一些简单的 cout 语句，以便在调用它们时输出一些信息(我假设您已经实现了这些方法)：

数组列表构造函数：n_element = n; cout << "Constructing the arrayList, n_element = " << n_element << endl;

小联盟球员构造器：cout << "Constructing a minor league player" << endl;

插入项方法：cout << "Inserting an item into the ArrayList" << endl;

下面是构建并运行上述代码后的输出：

Constructing the arrayList, n_element = 99
Constructing a minor league player
Inserting an item into the ArrayList

编辑 2 与进一步评论相关：

引用 elemType 的方法

例：

// this will basically just going to "hold" the BaseBallPlayer fetched
// from GetNextItem
BaseBallPlayer *bPlayer; 
playerList->GetNextItem(bPlayer);
cout << "Weight after fetching from list = " << bPlayer->weight << endl;

GetNextItem 的实现将如下所示：

void ArrayList<elemType>::GetNextItem(elemType& player) {
// implementation to get the next item in the array list
player = //... set the "NextItem" to the BaseBallPlayer reference we passed into this method
}

编辑3：print_player()多态性：

MinorLeaguePlayer *minPlayer = new MinorLeaguePlayer();
MinorLeaguePlayer *min2Player = new MinorLeaguePlayer();
MajorLeaguePlayer *majPlayer = new MajorLeaguePlayer();
MajorLeaguePlayer *maj2Player = new MajorLeaguePlayer();
playerList->InsertItem(minPlayer);
playerList->InsertItem(min2Player);
playerList->InsertItem(majPlayer);
playerList->InsertItem(maj2Player);
BaseBallPlayer *fetchedPlayer;
for (int i = 0; i < 4; i++) {
playerList->GetNextItem(fetchedPlayer);
fetchedPlayer->print_player();
}

请注意，在对其调用 print_player() 方法之前，您必须获取对 fetchedPlayer 的引用

playerList->GetNextItem(fetchedPlayer);
fetchedPlayer->print_player();

这是因为 GetNextItem 方法的结构方式是将 nextItem 的引用放在传递的 BaseBallPlayer 中。

下面是另一个示例，其中该方法将返回 BaseBallPlayer 而不是通过引用设置它：

method stub (in ArrayList):
elemType getNextItemReturn();
for loop:
for (int i = 0; i < 4; i++) {
playerList->getNextItemReturn()->print_player();
}

这是一个快速讨论的链接，询问哪个更有效率： 哪个更有效：返回值与按引用传递？

以及带有示例 cout 语句的输出：

Constructing the arrayList, n_element = 99
Inserting an item into the ArrayList
Inserting an item into the ArrayList
Inserting an item into the ArrayList
Inserting an item into the ArrayList
Printing From MINOR League Player
Player Name: MinorLeagueName Weight = 22
Printing From MINOR League Player
Player Name: MinorLeagueName Weight = 22
Printing From MAJOR League Player
Player Name: MajorLeaguePlayer Weight = 33
Printing From MAJOR League Player
Player Name: MajorLeaguePlayer Weight = 33

print_player() 的模拟实现：

void MinorLeaguePlayer::print_player() {
cout << "Printing From MINOR League Player" << endl;
cout << "Player Name: " << name << " Weight = " << weight << endl;
}
void MajorLeaguePlayer::print_player() {
cout << "Printing From MAJOR League Player" << endl;
cout << "Player Name: " << name << " Weight = " << weight << endl;
}

teamArrayList是指向BaseBallPlayer对象的指针列表。通过使用指针，它可以通过多态- 指针可以指向从BaseBallPlayer派生的任何类。

这是使用抽象基类的常用方法。然后，可以使用它来调用BaseBallPlayer类中的方法，并且将使用相应派生类中的实现。