Foreach loop with a pointer

Question

I have this constructor

class Vertex
{
    Vertex();
    ~Vertex();

    Edge* adjacencies;
};

I wanted there to be array of adjacencies, but it couldn't build. So I've created a pointer (Edge is my created class too).

And I have this piece of code with foreach loop that must iterate on all adjacencies, but, of course, it not compiles.

Vertex getted_vertex = vertexQueve.top();
for(Edge & e: getted_vertex.adjacencies)
            {
                Vertex v = Vertex(e._idFrom);
            }

Should I change the constructor or the loop?

Use std::vector and you can have everything you want from an array. — StoryTeller - Unslander Monica
– StoryTeller - Unslander Monica, Commented Apr 3, 2016 at 8:31

jpo38 · Accepted Answer · 2016-04-03 08:38:00Z

2

Simply use:

class Vertex
{
public:
    Vertex();
    ~Vertex();

    std::vector<Edge> adjacencies;
    // or std::vector<Edge*> adjacencies;
};

Fill it like that:

Vertex vertex;
vertex.adjacencies.push_back( Edge() );
// or vertex.adjacencies.push_back( new Edge() );

Later, to iterate on adjacencies:

Vertex vertex;
for ( std::vector<Edge>::const_iterator edge = vertex.adjacencies.begin();
      // or std::vector<Edge*>::const_iterator edge = vertex.adjacencies.begin();
      edge != vertex.adjacencies.end();
      ++edge )
{
    Edge& edgeRef = *edge;
    // simply use edgeRef

    // or Edge* edgePtr = *edge;
}

If storing Edge* in the vector, you may need to delete them from Vertex destructor.

edited Apr 3, 2016 at 8:38

answered Apr 3, 2016 at 8:32

jpo38

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1 Comment

Alan Stokes Over a year ago

You can still use a foreach / range for here as the OP wishes.

Paul Evans · Accepted Answer · 2016-04-03 08:32:43Z

2

You need your constructor and destructor to be public and a container for your edges, something like:

class Vertex
{
public:
    Vertex();
    ~Vertex();
private:
    vector<Edge> adjacencies;
};

answered Apr 3, 2016 at 8:32

Paul Evans

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Comments

Taimoor Mirza · Accepted Answer · 2016-04-03 08:48:21Z

0

1st, you have to place destructor, constructor in the public space and "adjancencies" in the private space. to create a dynamic array, you have to take its size first. then use this statement:

adjancencies = new Edge[i]l; // i refers to the size of the dynamic 1D array.

answered Apr 3, 2016 at 8:48

Taimoor Mirza

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