传递矢量 <vector<int> &gt;争论

Question

I'm new in C++ programming and for some time, I've been trying to resolve a problem with a vector<vector<int> > .

This is the header file

#ifndef ASSIGNMENT_H_
#define ASSIGNMENT_H_

#include <iostream>
#include <vector>
#include <string>

using std::string;
using std::vector;
using namespace std;

class Mood{
public:
   string lecture;
   vector<Block> blocks;

   Mood(vector<vector<int> > &m, string lecture){
     this->lecture=lecture;
     for(auto r: m){
        blocks.push_back(Block(r));
     }
  }
};
#endif

Block is another simple class with just 2 int written in the same file (but I think it not important for my problem).

The problem is in the main written in another file:

#include <iostream>
#include <vector>
#include <string>
#include "assignment.h"
using std::vector;
using std::string;
using namespace std;
int main(){
   Mood r= Mood({{1,2}},"Hello");
}

The error is very general: expected expression

Answer 1

Either you have stripped some important parts of the error message, or your compiler is exceptionally uncommunicative.

The handling of initializer lists is still sometimes a bit - erm - suboptimal. Please try this:

auto main() -> int {
   auto r = Mood({vector<int>{1,2}}, "Hello");
}

Update

In the comments we have found, that you use C++11 initialization syntax, but don't have C++11 support activated. Either activate C++11, or resort to the old approach to initialize vectors:

vector<vector<int> > m;
vector<int> m0;
m.push_back(m0);
m[0].push_back(1);
m[0].push_back(2);
Mood r = Mood(m, "Hello");

Answer 2

Try defining the argument m in the constructor as const, eg:

Mood(const vector<vector<int> > &m, string lecture)

This will allow you to pass in an R-Value (ie {{2,3}} )