C++ 编译器错误 "no matching function"

Question

这是涉及的两个函数:

int FixedLengthRecordFile :: write (const int numRec, const FixedLengthFieldsRecord & rec)
{
    /*** some code ***/

    return rec.write(file); // FILE* file is an attribute of FixedLengthRecordFile
}


int FixedLengthFieldsRecord :: write (FILE* file) { /* ... code ... */ }

我得到这个错误:

FixedLengthRecordFile.cpp: In member function ‘int FixedLengthRecordFile::write(int, const FixedLengthFieldsRecord&)’:
FixedLengthRecordFile.cpp:211:23: error: no matching function for call to ‘FixedLengthFieldsRecord::write(FILE*&) const’
FixedLengthRecordFile.cpp:211:23: note: candidate is:
FixedLengthFieldsRecord.h:35:7: note: int FixedLengthFieldsRecord::write(FILE*) <near match>
FixedLengthFieldsRecord.h:35:7: note:   no known conversion for implicit ‘this’ parameter from ‘const FixedLengthFieldsRecord*’ to ‘FixedLengthFieldsRecord*’
FixedLengthRecordFile.cpp:213:1: warning: control reaches end of non-void function [-Wreturn-type]

错误的原因是什么？我在代码中没有看到任何错误。此外，我还有另外两个类似的函数(write)，它工作得很好。

Answer 1

int FixedLengthRecordFile::write( const int numRec, 
                                  const FixedLengthFieldsRecord& rec)
{
   /*** some code ***/

    return rec.write(file); // FILE* file is an attribute of FixedLengthRecordFile
}


int FixedLengthFieldsRecord::write(FILE* file) 

您通过const 和const 引用传递参数，但是，您调用的函数rec.write(file) 不是const 函数，它可能会修改那些传入的对象，因此，编译器会报错。

您应该执行以下操作:

   int FixedLengthFieldsRecord::write(FILE* file)  const  
       // add const both declaration and definition ^^^