Where am I going wrong re: data validation c++ -

this question has answer here:

• using getline(cin, s) after cin 10 answers

i have code: wish take in id, make sure it's of 8 chars in length, make sure each digit number, , continue ask until give correct input. before marks down, researched , tried @ answers given :c don't why says id enter 00000002 invalid id according code. it's not working. can help?

void student::getdata(){     string id_;      cout << "lastname?" << endl;     cin >> lastname;      cout << "firstname?" << endl;     cin >> firstname;      cout << "id?" << endl;     while(getline(cin,id_) && id_.size() != 8){     cout << "invalid id" << endl;     } 

while(getline(cin,id_) && id_.size() != 8){ 

here getline() gets newline left on previous line of input. add line ignore rest of line before that.

cin.ingore(std::numeric_limits<std::streamsize>::max(), '\n'); while(getline(cin,id_) && id_.size() != 8){