Can not use template inside class?

Question

I try to implement a function which received parameter type int and string. So I though of template.

Header file

template <typename T>
class SymbolTable {
public:
   void run(string filename);
   void insert(T value);
}

Implementation (.cpp) file

template <typename T>
void SymbolTable::run(string filename)
{
   cout << "success" << endl;
}
// Haven't implement "insert" yet!

Compiler report error:

name followed by '::' must be a class or namespace name

If I remove template, It works fine. Any suggestion...?

Try `template void SymbolTable::run(string filename)`. Also see [Why can templates only be implemented in the header file?](https://stackoverflow.com/q/495021/3309790) — songyuanyao, Sep 09 '21 at 09:01
Your title talks about using templates *inside* a class. But your code shows a *class template*. Which is it? — Konrad Rudolph, Sep 09 '21 at 09:01
*"typo"*: -> `template void SymbolTable::run(string filename)`. — Jarod42, Sep 09 '21 at 09:01
Just make some edit in Header file. Sorry, It's my first post. — Tan Nguyen, Sep 09 '21 at 09:02
@TanNguyen In comparison to many other first posts yours is pretty good. You show all the code we need and the exact error. And everything as text! We don't see that too often on first posts :) — Lukas-T, Sep 09 '21 at 09:49

LNiederha · Answer 1 · 2021-09-09T10:27:38.277

3

This is just a basic syntax error. Your method definition should be:

template <typename T>
void SymbolTable<T>::run(string filename)
{
   cout << "success" << endl;
}

Should you need it, here are a few syntactically correct examples on how to use different variants of templates in c++.

edited Sep 09 '21 at 10:27

answered Sep 09 '21 at 09:06

LNiederha

1

cplusplus.com is not "the reference" but a (frequently pretty awful) site written by "enthusiasts". It's of little use unless you already know enough to tell the good bits from the bad bits. – molbdnilo Sep 09 '21 at 10:00
@molbdnilo Good call, thanks for the correction. I agree my phrasing was misleading... IMO your comment on that website is completely valid if not a little harsh. It is true is asks for a lot of technical knowledge to use it in full, but they have a lot of syntactically correct examples which is nice. But the reliability of sources is a whole other opinion-based discussion... – LNiederha Sep 09 '21 at 10:24
1

Reliability is not a matter of opinion, it is a matter of fact, and the issues are usually with semantics, not syntax. – molbdnilo Sep 09 '21 at 14:27
@molbdnilo Yeah your completely right... re-read my comment and the last sentence is pretty dumb... thanks for pointing all of that out! – LNiederha Sep 09 '21 at 14:35

1 Answers1