【移動(dòng)應(yīng)用開發(fā)技術(shù)】C++ 繼承（二）

【移動(dòng)應(yīng)用開發(fā)技術(shù)】C++繼承（二）

多態(tài)是一種泛型編程的思想，虛函數(shù)是其實(shí)現(xiàn)的手段（利用父類的指針指向子類的空間）。好了，開始正文->來一段基本代碼：#include

<iostream>

using

namespace

std;

class

CPeople

{

public:

virtual

void

goHome()

{

cout

<<

"

Go

Home"

<<

endl;

}

};

class

Aonaufly

:

public

CPeople

{

void

goHome()

{

cout

<<

"

Go

Wuhan"

<<

endl;

}

};

int

main()

{

CPeople

*

people_1

=

new

Aonaufly;

people_1->goHome();

delete

people_1;

return

0;

}運(yùn)行結(jié)果：解析：①虛函數(shù)的關(guān)鍵字是：virtual（定義格式：virtualvoidgoHome()）②子類中也有一個(gè)goHome函數(shù)，因?yàn)樵诟割愔術(shù)oHome函數(shù)是個(gè)虛函數(shù)。所以子類中的goHome與父類中的goHome形成了重寫。（虛函數(shù)形成重寫，普通函數(shù)形成覆蓋）③CPeople*people_1=newAonaufly;即用利用父類的指針指向子類的空間。（不能申明為棧，因?yàn)闂^(qū)隊(duì)形沒有指針概念）這種形式在C#/Java當(dāng)中也很常見④實(shí)際上在子類中的virtual可以省略不寫，編譯會(huì)自動(dòng)加上如果，在子類中不重寫虛函數(shù)：#include

<iostream>

using

namespace

std;

class

CPeople

{

public:

virtual

void

goHome()

{

cout

<<

"

Go

Home"

<<

endl;

}

};

class

Aonaufly

:

public

CPeople

{

};

int

main()

{

CPeople

*

people_1

=

new

Aonaufly;

people_1->goHome();

delete

people_1;

return

0;

}結(jié)果：解析：①因?yàn)樽宇悰]有重寫父類虛函數(shù)goHome，所以調(diào)用父類的goHome純虛函數(shù)->沒有實(shí)現(xiàn)的函數(shù)#include

<iostream>

using

namespace

std;

class

CPeople

{

public:

virtual

void

goHome()

=

0;

};

class

Aonaufly

:

public

CPeople

{

virtual

void

goHome()

{

cout

<<

"

Go

Wuhan"

<<

endl;

}

};

int

main()

{

CPeople

*

people_1

=

new

Aonaufly;

people_1->goHome();

delete

people_1;

return

0;

}結(jié)果:解析：①純虛函數(shù)virtualvoidgoHome()=0。一個(gè)父類中都是純虛函數(shù)，這個(gè)類就是接口類

；如果這個(gè)父類不全是純函數(shù)那這個(gè)父類就是抽象類。②有純虛函數(shù)的類，不能被實(shí)例化。只能通過繼承，在子類中實(shí)現(xiàn)（必須在子類中重寫）重點(diǎn)補(bǔ)充：①重寫虛函數(shù)，函數(shù)名稱/

函數(shù)參數(shù)列表/函數(shù)返回值類型必須是一樣（絕大部分情況）②特殊情況：#include

<iostream>

using

namespace

std;

class

CPeople

{

public:

virtual

CPeople&

goHome()

{

cout

<<

"

Go

Home"

<<

endl;

return

(*this);

}

};

class

Aonaufly

:

public

CPeople

{

virtual

Aonaufly&

goHome()

{

cout

<<

"

Go

Wuhan"

<<

endl;

return

(*this);

}

};

int

main()

{

CPeople

*

people_1

=

new

Aonaufly;

people_1->goHome();

delete

people_1;

return

0;

}結(jié)果：這是一個(gè)特殊的情況返回值不一樣也會(huì)構(gòu)成重寫，這個(gè)情況叫協(xié)變。虛析構(gòu)為了時(shí)子類，父類中的機(jī)構(gòu)函數(shù)都被調(diào)用，需要使用虛析構(gòu)（不然，只會(huì)調(diào)用父類的的）#include

<iostream>

using

namespace

std;

class

CPeople

{

public:

virtual

CPeople&

goHome()

{

cout

<<

"

Go

Home"

<<

endl;

return

(*this);

}

virtual

~CPeople()

{

cout

<<

"Cpeople"

<<

endl;

}

};

class

Aonaufly

:

public

CPeople

{

virtual

Aonaufly&

goHome()

{

cout

<<

"

Go

Wuhan"

<<

endl;

return

(*this);

}

~Aonaufly()

{

cout

<<

"Aonaufly"

<<

endl;

}

};

int

main()

{

CPeople

*

people_1

=

new

Aonaufly;

//people_1->goHome();

delete

people_1;

return

0;

}