Syntax of Declaring a Constructor in Header (.h) and then Defining in a Class File (.cpp) C++

Question

If anyone could lay this out, I would appreciate it. Example of what I thought would work (assume the needed #include statements are there):

//.h file
class someclass(){}

//.cpp
someclass::
    someclass(){
         //implementation
         // of 
         //class
};

Answer 1

someclass.h file

#ifndef SOME_CLASS_H
#define SOME_CLASS_H    

class someclass
{
public:
  someclass();  // declare default constructor

private:
  int member1; 
};

#endif

someclass.cpp

someclass::someclass()   // define default constructor
: member1(0)             // initialize class member in member initializers list
{
   //implementation
}

Answer 2

Header:

//.h file
class someclass
{
    someclass();
}; // <-- don't forget semicolon here

Source:

#include "someClass.h"
//.cpp
someclass::someclass()
{
    // Implementation goes here
} // <-- No semicolon here

Answer 3

You have to declare the constructor in your class if you want to provide a definition for it. You are only doing the second thing.

Also, your original class definition contains some mistakes: no parentheses are needed after the class name, and a semicolon is needed after the final curly brace.

class someclass
{
    someClass(); // Here you DECLARE your constructor
};

...

someclass::someclass() // Here you DEFINE your constructor
{
    ...
}