Expression for file operations using overloaded operators does not give expected results?

Question

I am trying to overload operators '+' and '=' for a customized class operating over files. The operator '+' overload appends the content of right operand file to left operand file. And operator '=' overload writes the contents of right operand file into left operand file. The operator overloads work fine independently but when combined in an expression they do not give expected results. With the expression in below program efile3 = (efile2+efile1) results in efile3 getting contents of only efile2's contents prior to appending. The efile2 is properly appended with efile1's content. Why the expression fails to give expected results? Does it have something to do with operator precedence?

     #include<fstream>
     #include<string>
    class EasyFile{
        std::string fileContent;
        std::string temp1,temp;
        char* filePath;
        public:
            EasyFile(char* filePath){
               this->filePath = filePath;
               std::ifstream file(filePath);
               int count=0;
               while(file){
                   getline(file,temp1);
                   count++;
               }
               count--;
               std::ifstream file1(filePath);
               while(count!=0){
                    getline(file1,temp1);
                    temp = temp + temp1+"\n";
                    count--;
               }
               setFileContent(temp);
            }

            void setFileContent(std::string line){
                fileContent = line;

            }

            char* getFilePath(){
                return filePath;
            }

            std::string getFileContent(){
                return fileContent;
            }

            void setContent(std::string content){
                std::ofstream file(filePath);
                file<<content;
            }
            void operator=(EasyFile f);
            EasyFile operator+(EasyFile f);
    };
    void EasyFile::operator=(EasyFile f){
        this->setContent(f.getFileContent());
    }
    EasyFile EasyFile::operator+(EasyFile f){
        EasyFile f1(this->getFilePath());
        std::string totalContent = f1.getFileContent()+f.getFileContent();
        f1.setContent(totalContent);
        return f1;
    }

    int main(int argc,char** argv)
    {
        EasyFile efile1(argv[1]);
        EasyFile efile2(argv[2]);
        EasyFile efile3(argv[3]);
        efile3 =(efile2+efile1);
        return 0;
    }

If someone elaborates over that down vote i will happily delete the question! Thank you! — Deepeshkumar, Oct 22 '15 at 11:51
Your code is both incomplete and contains too much irrelevant stuff. — melpomene, Oct 22 '15 at 11:51
@melpomene Neglect the irrelevant stuff. But incomplete? Both the operators behave fine independently. Just the expression fails. — Deepeshkumar, Oct 22 '15 at 11:56
@melpomene and what is the compiler error you are getting? Because your comment questions my integrity. — Deepeshkumar, Oct 22 '15 at 12:00
The example [does compile](http://coliru.stacked-crooked.com/a/e7d28aee215a2411) — maddouri, Oct 22 '15 at 12:01
@Deepeshkumar `try.cc:2:14: error: ‘string’ in namespace ‘std’ does not name a type` `std::string fileContent;` is the first one. — melpomene, Oct 22 '15 at 12:02
@melpomene See this. http://stackoverflow.com/questions/17040098/c-stdstring-has-not-been-declared-error .It has to do with the compiler you are using. string class is now part of namespace 'std'. — Deepeshkumar, Oct 22 '15 at 12:05
@Deepeshkumar See this. http://stackoverflow.com/a/17040165/1848654 Your code is missing `#include ` — melpomene, Oct 22 '15 at 12:06
@melpomene I did not include those lines because i thought that it is obvious for a programmer to know that i have included them while compiling at my side. — Deepeshkumar, Oct 22 '15 at 12:10
OK, next piece of missing information: How are you running the program? — melpomene, Oct 22 '15 at 12:14

maddouri · Accepted Answer · 2015-10-22T12:26:37.097

1

~~I think that you're not flushing the data to efile1, that's why efile3 gets only the "old" content.~~

EDIT: You should update your fileContent when setting the content:

Try this:

Run It Online !

// this method is called by `operator+()`
void setContent(std::string content){
    std::ofstream file(filePath);
    file << content;
    setFileContent(content);  // this should update `fileContent`
                              // which is read by `operator=()`
                              // when it calls `setContent(f.getFileContent())`
                              // thus actually updating the left-hand side of the operation
}

edited Oct 22 '15 at 12:26

answered Oct 22 '15 at 11:54

maddouri

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Thank you! That resolved the issue! Thank you very much! – Deepeshkumar Oct 22 '15 at 12:19
You're welcome. You can even play with the code online if you want (check out the "Run It Online" button). – maddouri Oct 22 '15 at 12:27
Thank you! Did not know this! – Deepeshkumar Oct 22 '15 at 12:30

Expression for file operations using overloaded operators does not give expected results?

1 Answers1