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序号：48321 发表者：wwww 发表日期：2003-07-30 12:17:23
<br>主题：函数声明int Fun() const 请问const代表什么意思？
<br>内容：函数声明int Fun() const 请问const代表什么意思？
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<font color=red>答案被接受</font><br>回复者：Fang 回复日期：2003-07-30 14:06:22
<br>内容：Constant Member Functions<BR>C++ Specific <BR><BR>Declaring a member function with the const keyword specifies that the function is a "read-only" function that does not modify the object for which it is called.<BR><BR>To declare a constant member function, place the const keyword after the closing parenthesis of the argument list. The const keyword is required in both the declaration and the definition. A constant member function cannot modify any data members or call any member functions that aren't constant.<BR><BR>END C++ Specific<BR><BR>Example<BR><BR>// Example of a constant member function<BR>class Date<BR>{<BR>public:<BR>&nbsp;&nbsp; Date( int mn, int dy, int yr );<BR>&nbsp;&nbsp; int getMonth() const;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; // A read-only function<BR>&nbsp;&nbsp; void setMonth( int mn );&nbsp;&nbsp;&nbsp;&nbsp;// A write function;<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; //&nbsp;&nbsp;&nbsp;&nbsp;cannot be const<BR>private:<BR>&nbsp;&nbsp; int month;<BR>};<BR><BR>int Date::getMonth() const<BR>{<BR>&nbsp;&nbsp; return month;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;// Doesn't modify anything<BR>}<BR>void Date::setMonth( int mn )<BR>{<BR>&nbsp;&nbsp; month = mn;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;// Modifies data member<BR>}<BR>
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