C++ : constructor initialization list

In the implementation of the constructor, it is possible to initialize internal members with an initialization list. It is basically a list of parameters following a semicolon (:) with their initialization values :

Basic initialization

class Something
{
private:
    int m_nValue;
    double m_dValue;
    int *m_pnValue;

public:
    Something()
    {
        m_nValue = 0;
        m_dValue = 0.0;
        m_pnValue = 0;
    }
};

With an initialization list

class Something
{
private:
    int m_nValue;
    double m_dValue;
    int *m_pnValue;

public:
    Something() : m_nValue(0), m_dValue(0.0), m_pnValue(0)
    {
    }
};

Note : This syntax can be used with const member as well. For instance, if m_nValue was a const, it would had the same effect.

Cem SOYDING

Author & Editor

Senior software engineer with 12 years of experience in both embedded systems and C# .NET