C++纯虚const成员函数
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C++ pure virtual const member function
提问by Chin
How can I declare a pure virtual member function that is also const? Can I do it like this?
如何声明一个也是 const 的纯虚成员函数？我可以这样做吗？
virtual void print() = 0 const;
or like this?
或者像这样？
virtual const void print() = 0;
回答by raina77ow
From Microsoft Docs:
来自微软文档：
To declare a constant member function, place the
constkeyword after the closing parenthesis of the argument list.
要声明常量成员函数，请将
const关键字放在参数列表的右括号之后。
So it should be:
所以应该是：
virtual void print() const = 0;
回答by Adam Rosenfield
Only the virtual void print() const = 0form is acceptable. Take a look at the grammar specification in C++03 §9/2:
只有virtual void print() const = 0表格是可以接受的。看看 C++03 §9/2 中的语法规范：
member-declarator:
declarator pure-specifieropt
declarator constant-initializeropt
identifieropt:constant-expressionpure-specifier:
= 0
member-declarator:
declarator pure-specifier opt
declarator constant-initializer opt
identifier opt:constant-expression纯说明符：
= 0
The constis part of the declarator-- it's the cv-qualifier-seqoptin the direct-declarator(§8/4):
该const是金声明符-它的CV限定符序列选择在直接说明符（§8/ 4）：
declarator:
direct-declarator
ptr-operator*declarator*direct-declarator:
declarator-id
direct-declarator(parameter-declaration-clause)cv-qualifier-seqoptexception-specificationopt
direct-declarator[constant-expressionopt]
(declarator)
declarator:
直接声明
符 ptr-operator*declarator*direct-declarator:
declarator-id
direct-declarator(parameter-declaration-clause)cv-qualifier-seq optexception-specification opt
direct-declarator[constant-expression opt]
(declarator)
Hence, the = 0must come after the const.
因此，= 0必须在 之后const。
回答by π?ντα ?ε?
Of course you can. The correct syntax is:
当然可以。正确的语法是：
virtual void print() const = 0;
回答by Rahul Tripathi
Try this:-
尝试这个：-
virtual void print() const = 0;
