{{< Concepts >}}

Make Method Static

Constraints

• There shall not be calls to instance methods. Convert them to static.
• The method shall be private. (Makes introduce parameter easier. TODO: remove this constraint)

Recipe

1. For each reference to an instance variable, apply Introduce Parameter.

For example,

class Foo {
    void Bar() const;
    int m_width;
};
 
void Foo::Bar() const
{
    cout << m_width;
}
 
foo.Bar();
pFoo->Bar();

Becomes:

class Foo {
    void Bar(int width) const;
    int m_width;
};
 
 
void Foo::Bar(int width) const
{
    cout << width;
}
 
foo.Bar(m_width);
pFoo->Bar(m_width);

2. Find All References

This is hard. VisualAssist sometimes gets it wrong.

3. Remove const, add static, fix all callers, replacing member access operators . and -> with the scope resolution operator.

Should this be multiple steps? How can we do this incrementally, in case there are lots of callers? Probably need to add a set-up step where we create a delegating thunk for a while, which we will clean up later.

class Foo {
    static void Bar(int width);
    int m_width;
};
 
void Foo::Bar(int width)
{
    cout << width;
}
 
Foo::Bar(m_width);
Foo::Bar(m_width);

4. Change it to a free function.

Provided that the static function does not use any private features of the original class, change it to a free function. Move the declaration from the class to just after the class, remove static. At the definition remove the scope. Remove the scope resolution operators at each call site.

class Foo {
};
void Bar(int width);
 
void Bar(int width)
{
    cout << width;
}
 
 
Bar(m_width);
Bar(m_width);

5. Move the free function to a namespace

Consider whether the free function should be in some namespace and move it there if so. Note: Generally the function should be in the same namespace as the types it operates on, which is often the global namespace. Some other times a local, anonymous namespace is a good idea.