它何时通过两次while循环

Question

I have trying parse a text file called FileName that looks like:

KD JD 6s 5s 3c // no rank (king high)
AH Ks Js AD Ac // three of a kind

Now I wanna store them into a vector (everything before "//").

int FileParsing(vector<Card> & v, char * FileName) {
    ifstream ifs;
    ifs.open(FileName);
    if (!ifs.is_open()){
        cout << "file cannot be opened." << endl;
    } else {        
        string line;                    
        while(getline(ifs, line)){
            istringstream iss (line); 
            bool condition = CountWords(line); //dont worry about this method   
            ReadCardDefinitionStrings (condition, line, v);
        }       
    }
    return 0;
}


void ReadCardDefinitionStrings (bool condition, string line, vector<Card> & v){
    istringstream iss (line);   
    string CardDefinitionStrings;   //e.g. 2C, 3h, 7s, Kh
    if (condition) {
            while(iss>>CardDefinitionStrings){  
            if (CardDefinitionStrings == "//"){ //stop reading after it sees "//"
                return;
            }
            Card c = TestCard(CardDefinitionStrings);
            v.push_back(c);     
        }
    }
}

The problem I am getting is: when it sees "//" after 3c, it goes back to

    while(getline(ifs, line)){
        istringstream iss (line); 
        bool condition = CountWords(line);  
        ReadCardDefinitionStrings (condition, line, v);
    }

But this time, line is empty (I wanted it to be: AH Ks Js AD Ac // three of a kind), which means this loop runs one time without doing anything. And the next run, line would be equal to AH Ks Js AD Ac // three of a kind. Any idea why this happens?

Answer 1

I think you forgot to put a lot of code up (card definitions and the like). And, from what I could tell, you had a couple of redundant definitions in some places.

However, I've implemented what you want (the ability to parse a text file called FileName that looks like):

KD JD 6s 5s 3c // no rank (king high)
AH Ks Js AD Ac // three of a kind

Assuming the input filestream has been initialized with the Filename:

ifstream ifs(FileName);

if (!ifs.is_open()) {
    cout << "file cannot be opened." << endl;
}
else {
    string line;

    //getline reads up until the newline character
    //but you want the characters up to "//"
    while(std::getline(ifs, line)) {

        //line has been read, now get rid of the "//"
        string substr = line.substr(0,line.find("//"));

        //assign the substr to an input stringstream
        istringstream iss(substr);

        //this will hold your card
            //NOTE: Since I don't have your implementation of Card, I put it as a string instead for demonstration purposes
        string card;

        //keep reading until you've read all the cards in the substring (from line)
        while (iss >> card) {
            v.push_back(card);//store the card in the vector
            cout << card << endl;//now output it to verify that the cards were read properly
        }

        cout << endl;//this is just for spacing - so it'll help us distinguish cards from different lines (in the output)
    }
    ifs.close();
}

Output:

KD
JD
6s
5s
3c

AH
Ks
Js
AD
Ac

Which is what you want. ;)