如何在另一个类中访问一个类的成员函数？

Question

我无法在另一个类中访问一个类的成员函数,尽管我可以在main()中访问它.我一直试图改变现状,但我无法理解我做错了什么.任何帮助,将不胜感激.

以下是生成错误的行:

cout << "\n\nRetrieve key from inside Envelope class: " << e.getData() << "\n\n";

以下是代码:

class Record{
  private:
    string key;
  public:
    Record(){ key = ""; }
    Record(string input){ key = input; }
    string getData(){ return key; }
    Record operator= (string input) { key = input; }
};

template<class recClass>
class Envelope{
  private:
    recClass * data;
    int size;

  public:
    Envelope(int inputSize){
      data = new recClass[inputSize];
      size = 0;
    }
    ~Envelope(){ delete[] data; }
    void insert(const recClass& e){
      data[size] = e;
      cout << "\n\nRetrieve key from inside Envelope class: " << e.getData() << "\n\n";
      ++size;
    }
    string getRecordData(int index){ return data[index].getData(); }
};

int main(){

  Record newRecord("test");
  cout << "\n\nRetrieve key directly from Record class: " << newRecord.getData() << "\n\n";

  Envelope<Record> * newEnvelope = new Envelope<Record>(5);
  newEnvelope->insert(newRecord);
  cout << "\n\nRetrieve key through Envelope class: " << newEnvelope->getRecordData(0) << "\n\n";

  delete newEnvelope;
  cout << "\n\n";
  return 0;
}

Answer 1

您e作为常量引用传递void insert(const recClass& e){
然后您正在调用getData()未声明为常量的方法().

您可以通过重写getData()这样修复它:

string getData() const{ return key; }

Answer 2

您必须声明getData()为const可以从const上下文中调用它.你的insert功能需要const recClass& e你想要这样做Record:

string getData() const { return key; }