[英]C++ Member Reference base type 'Vertex *const' is not a structure or union
I am running into trouble trying to access the methods of an object stored in a vector. 尝试访问存储在向量中的对象的方法时遇到麻烦。 I know that getEdges returns an unordered map of edge but I am missing something with how to reference a Vertex object from within a vector.
我知道getEdges返回边缘的无序贴图,但是我缺少如何从向量中引用Vertex对象的东西。 Help?
救命?
In void UndirectedGraph::minSpanningTree(): 在void UndirectedGraph :: minSpanningTree()中:
std::vector<Vertex*> visited;
if(vertices.begin() != vertices.end())
{
visited.push_back(vertices.begin()->second);
visited[0]->distance = 0;
}
else
{
return;
}
std::vector<Vertex*>::const_iterator vit;
vit = visited.begin();
std::unordered_map<std::string, Edge> edges;
edges = vit -> getEdges();
In const std::unordered_map & Vertex::getEdges() const: 在const std :: unordered_map和Vertex :: getEdges()const中:
return edges;
The error: 错误:
UndirectedGraph.cpp:112:21: error: member reference base type 'Vertex
*const' is
not a structure or union
edges = vit -> getEdges();
~~~ ^ ~~~~~~~~ 1 error generated.
--EDIT-- - 编辑 -
Changing 更改
edges = vit -> getEdges();
to 至
edges = *(vit)->getEdges();
gave me the same error. 给了我同样的错误。
vit
is an iterator. vit
是一个迭代器。 Iteratirs work like pointers to container elements. 迭代的工作方式类似于指向容器元素的指针。 Your container element type is
Vertex*
. 您的容器元素类型为
Vertex*
。 Therefore vit
works like Vertex**
. 因此,
vit
工作方式类似于Vertex**
。
To call a member function given a Vertex** p
you would have to get to a Vertex*
first. 要调用给定
Vertex** p
的成员函数,您必须先进入Vertex*
。 This can be done by dereferencing p
like this: 可以这样取消
p
的引用:
(*p)
and at this point you can call your member function like 现在您可以像这样调用您的成员函数
(*p)->getEdges()
Iterators are no different. 迭代器没有什么不同。
Note 注意
*(p)->getEdges()
is totally different from the above (and wrong). 与上述完全不同(而且是错误的)。 It is the same as
与...相同
*((p)->getEdges())
and 和
(p)->getEdges()
is the same as 是相同的
p->getEdges()
which is known not to work. 这是行不通的。
On a related note, if you are using raw pointers you are probably doing it wrong. 与此相关的是,如果使用原始指针,则可能做错了。 You should either store
Vertex
objects directly in an std::vector<Vertex>
or use shared_ptr
or unique_ptr
in lieu of raw pointers. 您应该将
Vertex
对象直接存储在std::vector<Vertex>
或者使用shared_ptr
或unique_ptr
代替原始指针。
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