I have a problem with linker. I am trying to create template Tree but since I'm having some problems with using templates (my first time) I decided to do a "test template program". I have been looking for anserws before posting and tried some solutions posted on the forum but none has worked for me. Here is the test program:  .h file  #pragma once template &lt;class T&gt; class Node { public:     Node();     Node(T value);     ~Node();     void manualTree(); private:     T data;     Node *left, *right, *parent; };   .cpp file  #include "stdafx.h" #include &lt;iostream&gt; #include "Node.h" using namespace std;  template&lt;class T&gt; Node&lt;T&gt;::Node(T val) {     data = val; }  template&lt;class T&gt; void Node&lt;T&gt;::manualTree() {     Node* root = new Node(1);     root-&gt;left = new Node(2);     root-&gt;right = new Node(3);     cout &lt;&lt; "left : " &lt;&lt; root-&gt;left-&gt;data &lt;&lt; endl;     cout &lt;&lt; "right : " &lt;&lt; root-&gt;right-&gt;data &lt;&lt; endl;     cout &lt;&lt; "root : " &lt;&lt; root-&gt;data &lt;&lt; endl;  }  template class Node&lt;int&gt;;   main body  #include "stdafx.h" #include "arithmetics.h" #include &lt;iostream&gt; #include "Node.h" using namespace std;  int main() {     Node&lt;int&gt; n;     n.manualTree();     return 0; }   Here is what i get after trying to call manualTree() function: Severity    Code    Description Project File    Line    Column  Suppression State  Error   LNK1120 2 unresolved externals  zad6 - szablony C:\Users\Piotr\source\repos\zad6 - szablony\Debug\zad6 - szablony.exe   1   1    Error   LNK2019 unresolved external symbol "public: __thiscall Node&lt;int&gt;::~Node&lt;int&gt;(void)" (??1?$Node@H@@QAE@XZ) referenced in function _main  zad6 - szablony C:\Users\Piotr\source\repos\zad6 - szablony\zad6 - szablony\main.obj    1   1    Error   LNK2019 unresolved external symbol "public: __thiscall Node&lt;int&gt;::Node&lt;int&gt;(void)" (??0?$Node@H@@QAE@XZ) referenced in function _main   zad6 - szablony C:\Users\Piotr\source\repos\zad6 - szablony\zad6 - szablony\main.obj    1   1      EDIT:  I have moved everything to the .h file, like they said in the linked post and i still get the same warnings sometimes with a few more. Already tried putting into .cpp file these lines and still not working (with the same warnings):  template class Node&lt;int&gt;;   or  Node&lt;int&gt; n;   new .h file  #pragma once template &lt;class T&gt; class Node { public:     Node();     Node(T value) {         data = value;     }     ~Node();     void manualTree() {         Node* root = new Node(1);         root-&gt;left = new Node(2);         root-&gt;right = new Node(3);         cout &lt;&lt; "left : " &lt;&lt; root-&gt;left-&gt;data &lt;&lt; endl;         cout &lt;&lt; "right : " &lt;&lt; root-&gt;right-&gt;data &lt;&lt; endl;         cout &lt;&lt; "root : " &lt;&lt; root-&gt;data &lt;&lt; endl;      } private:     T data;     Node *left, *right, *parent; };
Quote from :     The only portable way of using templates at the moment is to implement them in header files by using inline functions.   Why is this?  (Clarification: header files are not the only portable solution. But they are the most convenient portable solution.)
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