blocks|key|1169996|text|您需要声明至少一个纯虚拟方法，例如：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1169997|class+Car+{
++++int+weight;
public:
++++Car(int+input)+{
++++++++weight+=+input;
++++}
++++void+sayVroem()+{
++++++++std::cout+<<+"Vroem...";
++++}
++++virtual+void+ImAPureVirtualMethod()+=+0;
};|code-block|syntax|javascript|1169998|如果您没有虚拟方法|1169999|class+Car+{
++++int+weight;
++++public:
++++++++void+sayVroem()+{
++++++++++++std::cout+<<+"Vroem...";
++++++++}
+++protected:+
++++++Car+()+=+default;
};|1170000|或者使析构函数成为纯虚拟的|1170001|class+Car+{
++++int+weight;
++++public:
++++++++Car(int+input)+{
++++++++++++weight+=+input;
++++++++}
++++++++void+sayVroem()+{
++++++++++++std::cout+<<+"Vroem...";
++++++++}
++++++++virtual+~Car()+=+0;
};|1170002|在使用虚拟析取器时，需要注意的一件事是，当一个派生类被销毁时，它将调用基类descructor，因此您需要提供一个实现，例如：|1170003|inline+Car::~Car()+{+}|1170004|有很多东西描述这一点：|1170005|班级|offset|length|1170006|https://www.geeksforgeeks.org/pure-virtual-functions-and-abstract-classes/|1170007|entityMap|0|LINK|mutability|MUTABLE|url|https://en.cppreference.com/w/cpp/language/abstract_class|1^0|0|0|0|0|0|0|0|0|0|0|2|0|0|0|22|1|0^^$0|@$1|2|3|4|5|6|7|19|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|1A|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|1B|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|1C|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|1D|8|@]|9|@]|A|$]]|$1|M|3|N|5|D|7|1E|8|@]|9|@]|A|$E|F]]|$1|O|3|P|5|6|7|1F|8|@]|9|@]|A|$]]|$1|Q|3|R|5|D|7|1G|8|@]|9|@]|A|$E|F]]|$1|S|3|T|5|6|7|1H|8|@]|9|@]|A|$]]|$1|U|3|V|5|6|7|1I|8|@]|9|@$W|1J|X|1K|1|1L]]|A|$]]|$1|Y|3|Z|5|6|7|1M|8|@]|9|@$W|1N|X|1O|1|1P]]|A|$]]|$1|10|3|-4|5|6|7|1Q|8|@]|9|@]|A|$]]]|11|$12|$5|13|14|15|A|$16|17]]|18|$5|13|14|15|A|$16|Z]]]]

You need to declare at least one method pure virtual, like:

<pre><code>class Car {
 int weight;
public:
 Car(int input) {
 weight = input;
 }
 void sayVroem() {
 std::cout &lt;&lt; "Vroem...";
 }
 virtual void ImAPureVirtualMethod() = 0;
};
</code></pre>

If you have no virtual methods

<pre><code>class Car {
 int weight;
 public:
 void sayVroem() {
 std::cout &lt;&lt; "Vroem...";
 }
 protected: 
 Car () = default;
};
</code></pre>

Or by making the destructor pure virtual like 

<pre><code>class Car {
 int weight;
 public:
 Car(int input) {
 weight = input;
 }
 void sayVroem() {
 std::cout &lt;&lt; "Vroem...";
 }
 virtual ~Car() = 0;
};
</code></pre>

One thing to be aware of when using virtual descructors is that when a derived class is destroyed it will call the base class descructor so you will need to provide an implementation, for example: 

<pre><code>inline Car::~Car() { }
</code></pre>

There are plenty of stuff out there describing this:

<a href="https://en.cppreference.com/w/cpp/language/abstract_class" rel="nofollow noreferrer">https://en.cppreference.com/w/cpp/language/abstract_class</a>

<a href="https://www.geeksforgeeks.org/pure-virtual-functions-and-abstract-classes/" rel="nofollow noreferrer">https://www.geeksforgeeks.org/pure-virtual-functions-and-abstract-classes/</a>

blocks|key|1802867|text|你试过在网上搜索吗？我不使用C%2B%2B，但这项研究似乎相当容易，而且有很多答案。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1802868|C%2B%2B抽象类的IBM解释|offset|length|1802869|C%2B%2B编程/类/抽象类|1802870|entityMap|0|LINK|mutability|MUTABLE|url|https://www.ibm.com/support/knowledgecenter/en/SSLTBW_2.3.0/com.ibm.zos.v2r3.cbclx01/cplr142.htm|1|https://en.wikibooks.org/wiki/C%252B%252B_Programming/Classes/Abstract_Classes^0|0|0|C|0|0|0|B|1|0^^$0|@$1|2|3|4|5|6|7|R|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|S|8|@]|9|@$D|T|E|U|1|V]]|A|$]]|$1|F|3|G|5|6|7|W|8|@]|9|@$D|X|E|Y|1|Z]]|A|$]]|$1|H|3|-4|5|6|7|10|8|@]|9|@]|A|$]]]|I|$J|$5|K|L|M|A|$N|O]]|P|$5|K|L|M|A|$N|Q]]]]

Have you tried searching online ? 
I'm not using C++ but the research seems pretty easy and with plenty of answers. 

<a href="https://www.ibm.com/support/knowledgecenter/en/SSLTBW_2.3.0/com.ibm.zos.v2r3.cbclx01/cplr142.htm" rel="nofollow noreferrer">IBM Explanation of C++ abstract classes</a>

<a href="https://en.wikibooks.org/wiki/C%2B%2B_Programming/Classes/Abstract_Classes" rel="nofollow noreferrer">Wikibooks - C++ Programming/Classes/Abstract Classes</a>

blocks|key|1170057|text|最简单的显式方法是将所有构造函数声明为受保护的=>，这样即使没有纯虚拟成员，也无法实例化类。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1170058|就你而言：|1170059|class+Car+{
++++int+weight;
protected:+//+only+derived+classes+can+access+those+functions
++++Car(int+input)+{
++++++++weight+=+input;
++++}
++++//+if+you+just+have+the+default+c-tor+you+can+move+it+to+protected+like+this:
++++Car()+=+default;
public:
++++void+sayVroem()+{
++++++++std::cout+<<+"Vroem...";
++++}
++++//+feel+free+to+add+virtual+methods+later+on+if+required
};|code-block|syntax|javascript|1170060|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|L|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|M|8|@]|9|@]|A|$G|H]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

The easiest way to do this explicitly is to declare all constructors as protected => Then you won't be able to instantiate the class even without pure virtual members.

In your case:

<pre class="lang-cpp prettyprint-override"><code>class Car {
 int weight;
protected: // only derived classes can access those functions
 Car(int input) {
 weight = input;
 }
 // if you just have the default c-tor you can move it to protected like this:
 Car() = default;
public:
 void sayVroem() {
 std::cout &lt;&lt; "Vroem...";
 }
 // feel free to add virtual methods later on if required
};
</code></pre>

Having been taught Java, I am confused by how Object Orientation is implemented in C++.

Having this class:

<pre><code>class Car {
 int weight;
public:
 Car(int input) {
 weight = input;
 }
 void sayVroem() {
 std::cout &lt;&lt; "Vroem...";
 }
};
</code></pre>

In Java I would be able to declare this an abstract class by declaring it as <code>public abstract class Car</code>. This would result in that the class cannot be instantiated. Is something similar possible in c++?

How to declare abstract classes in c++

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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在学习了Java之后，我对如何在C++中实现面向对象感到困惑。有这门课：class Car { int weight;public: Car(int input) { weight = input; } void sayVroem() { std::cout << "...

问如何在c++中声明抽象类
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