c++ - 构造函数中缺少表达式

我有以下课程：

  class BandMember
{
private:
    char *name;
    int age;
    int relationshipStatus;
    char *musicianType;
public:
    //functions
    void setName(char* name1);
    char * getName() const;
    void setAge(int age1);
    int getAge() const;
    void setRelationshipStatus(int status);
    int getRelationshipStatus() const;
    void setMusicianType(char* job);
    char* getMusicianType() const;
    BandMember* readBandMember();
    //print
    void print();

    //constructor
    BandMember(const char *nameToAdd = "no name", const int ageToAdd = 0,
        const int relationshipStatusToAdd = 0,
        const char *musicianTypeToAdd = "no music type");

    //destructor
    ~BandMember() { delete[] name; delete[] musicianType;}

    //copy constructor
    BandMember(const BandMember& bandMember);
};

在BandMember* BandMember::readMember中的代码是：

 BandMember* BandMember::readBandMember()
{
    char *nameNewMember, *musicTypeNewMember;
    int ageNewMember, familyStatusNewMember;

    nameNewMember = new char[NAME_LENGTH];
    musicTypeNewMember = new char[NAME_LENGTH];

    cin.ignore(10,'\n');
    cout << "Enter band member name: ";   //askName() - TODO
    cin.getline(nameNewMember, NAME_LENGTH);
    reallocate(nameNewMember, strlen(nameNewMember));

    cout << "enter the age of the band member: ";  //askAge - TODO
    cin >> ageNewMember;

    cin.ignore(10,'\n');
    cout << "enter musician type: ";     //askMusicianType - TODO
    cin.getline(musicTypeNewMember, NAME_LENGTH);
    reallocate(musicTypeNewMember, strlen(musicTypeNewMember));

    return new BandMember(nameNewMember, ageNewMember,,musicTypeNewMember);

问题出在返回值上。
编译器说“缺少表达式，重载+1”：
但是当我放return new BandMember(nameNewMember, ageNewMember,0,musicTypeNewMember);
该代码工作正常...
我不明白为什么。
我用默认值定义了一个默认承包商，所以当我返回一个缺少值时为什么它不起作用？

最佳答案

似乎您误解了默认参数在C ++中的工作方式...

您不能跳过参数并将其设置为默认值。如果要提供后面的参数，则需要在其前面提供所有参数。

因此，带双逗号的BandMember(nameNewMember, ageNewMember,,musicTypeNewMember)是不正确的，还必须提供relationshipStatusToAdd参数：

return new BandMember(nameNewMember, ageNewMember,0,musicTypeNewMember);
//                                                ^
// Added argument here --------------------------/

关于c++ - 构造函数中缺少表达式，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/59036147/