Templates and nested classes/structures
I have a simple container :
template <class nodeType> list {
public:
struct node {
nodeType info;
node* next;
};
//...
};
Now, there is a function called _search
which searches the list and returns a reference to the node which matched. Now, when I am referring to the return-开发者_开发百科type of the function, I think it should be list<nodeType>::node*
. Is this right? When I define the function inline, it works perfectly:
template <class nodeType> list {
public:
struct node {
nodeType info;
node* next;
};
node* _search {
node* temp;
// search for the node
return temp;
}
};
But, if I define the function outside the class,
template <class nodeType> list<nodeType>::node* list<nodeType>::_search() {
//function
}
it doesn't work. The compiler gives an error saying Expected constructor before list<nodeType>::_search
or something. The error is something similar to this. I don't have a machine on which I can test it currently.
Any help is sincerely appreciated.
that's because node
is a dependent type. You need to write the signature as follows (note that I have broken it into 2 lines for clarity)
template <class nodeType>
typename list<nodeType>::node* list<nodeType>::_search()
{
//function
}
Note the use of the typename
keyword.
You need to tell the compiler that node
is a type using the keyword typename
.Otherwise it will think node as a static
variable in class list
. Add typename
whenever you use node as a type in your implementation of list.
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