c – object.operator有什么作用？

发布时间：2020-12-16 10:24:53 所属栏目：百科来源：网络整理

导读：参见英文答案 Why does explicitly calling operator on std::cout cause unexpected output?????????????????????????????????????2个我看到了以下代码： cout.operator ("Hello"); 并认为它将是相同的： cout "Hello"; 但它打印： 0x46e030 它是如何工作

参见英文答案 > Why does explicitly calling operator<< on std::cout cause unexpected output?????????????????????????????????????2个
我看到了以下代码：

cout.operator << ("Hello");

并认为它将是相同的：

cout << "Hello";

但它打印：

0x46e030

它是如何工作的？它能做什么？

解决方法

object.operator<≤(？);与std :: ostream :: operator<<(std :: ostream&,??)不完全相同,因为它排除了非成员(免费)函数. std :: ostream :: operator<<成员是：

basic_ostream& operator<<( short value );
basic_ostream& operator<<( unsigned short value );
basic_ostream& operator<<( int value );
basic_ostream& operator<<( unsigned int value );
basic_ostream& operator<<( long value );
basic_ostream& operator<<( unsigned long value );
basic_ostream& operator<<( long long value );
basic_ostream& operator<<( unsigned long long value );
basic_ostream& operator<<( float value );
basic_ostream& operator<<( double value );
basic_ostream& operator<<( long double value );
basic_ostream& operator<<( bool value );
basic_ostream& operator<<( const void* value );
basic_ostream& operator<<( std::basic_streambuf<CharT,Traits>* sb);
basic_ostream& operator<<( basic_ostream& st,std::ios_base& (*func)(std::ios_base&) );
basic_ostream& operator<<( basic_ostream& st,std::basic_ios<CharT,Traits>& (*func)(std::basic_ios<CharT,Traits>&) );
basic_ostream& operator<<( basic_ostream& st,std::basic_ostream& (*func)(std::basic_ostream&) );

缺少const char *可能看起来令人困惑,但回想一下,你可以添加自由运算符<<除了上述成员之外,还有其他功能. < ostream的>包括这些：

ostream& operator<<( ostream& os,CharT ch );
ostream& operator<<( ostream& os,char ch );
ostream& operator<<( ostream& os,signed char ch );
ostream& operator<<( ostream& os,unsigned char ch );
ostream& operator<<( ostream& os,const CharT* s );
ostream& operator<<( ostream& os,const char* s );
ostream& operator<<( ostream& os,const signed char* s );
ostream& operator<<( ostream& os,const unsigned char* s );
template< class T >
ostream& operator<<( ostream&& os,const T& value );

通过专门调用object.operator<<(??)重载,你明确告诉它不要使用自由函数,只使用成员函数. “HELLO”的最佳匹配是void *重载,因此它打印了字符串的地址.

（编辑：李大同）

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