在课堂上访问私人会员？ [关闭]

Question

为什么我们必须先复制然后使用getfunction？为什么我们可以像borrowers.getID() == ID一样直接使用get函数而不是borrow.getID() == ID？

我只需要一个解释。我知道有些东西可能会丢失，但我在这里很困惑，因为它看起来效率不高！

class ReadershipList {
private:
    ifstream myin;
    ofstream myout;
    string readerfile;
    vector<Borrower> borrowers;
public:
    int findBorrowerbyID(string ID); //Find the borrowers index by ID
    int findBorrowerbyName(string name);
    void addBorrower(Borrower newBorrow); //Add a borrower to the vector of borrowers
    void listBorrowers(); //Prints the list of borrowers
    bool deleteBorrower(string ID); //Delete borrower using ID
    Borrower getBorrowerbyID(string ID); /
    Borrower getBorrowerbyName(string name); //Get borrower details using name
};

为什么我不能直接访问会员？

而不是使用这个：

bool ReadershipList::deleteBorrower(string ID) {
    Borrower borrow;
    for (int b = 0; b < borrowers.size(); b++) {
        borrow = borrowers[b];
        if (borrow.getID() == ID) {
            borrowers.erase(borrowers.begin() + b);
            return true;
        }
    }
    return false;
}

Answer 1

你不需要复制，你可以做

bool ReadershipList::deleteBorrower(string ID) {
    for (int b = 0; b < borrowers.size(); b++) {
        if (borrowers[b].getID() == ID) {
            borrowers.erase(borrowers.begin() + b);
            return true;
        }
    }
    return false;
}

要么

bool ReadershipList::deleteBorrower(string ID) {
    for (int b = 0; b < borrowers.size(); b++) {
        Borrower & borrow = borrowers[b]; // or better "const Borrower & borrow = borrowers[b];" if "string Borrower::getID() const"

        if (borrow.getID() == ID) {
            borrowers.erase(borrowers.begin() + b);
            return true;
        }
    }
    return false;
}