Question about function in C ++

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I have read the following C ++ code:

CEnumContext::CEnumContext(void)
: m_SearchContainer(NULL)
, m_SearchPattern(NULL)
, m_fileTimeFrom(0)
, m_fileTimeTo(0)
, m_FileFlags(FILE_ATTRIBUTE_NORMAL)
, m_maxDepth(-1)
, m_depth(0)
{
m_maxFileSize.QuadPart = 0;
m_SearchPattern = _tcsdup(TEXT("*.*"));
}

: m_SearchContainer(NULL)
, m_SearchPattern(NULL)
, m_fileTimeFrom(0)
, m_fileTimeTo(0)
, m_FileFlags(FILE_ATTRIBUTE_NORMAL)
, m_maxDepth(-1)
, m_depth(0) are variables.
I do not understand what they use here for and the purpose.
Help me explain them! thanks.

What I have tried:

: m_SearchContainer(NULL)
, m_SearchPattern(NULL)
, m_fileTimeFrom(0)
, m_fileTimeTo(0)
, m_FileFlags(FILE_ATTRIBUTE_NORMAL)
, m_maxDepth(-1)
, m_depth(0) are variables.
I do not understand what they use here for and the purpose.
Help me explain them! thanks.

Posted 2-Sep-19 18:24pm

Member 14221041

Updated 2-Sep-19 23:14pm

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KarstenK · Answer 1 · 2019-09-02T21:10:00

Solution 1

This is C++ syntax for constructor initialization of members. Some explanation and examples from Microsoft.

Posted 2-Sep-19 21:10pm

KarstenK

Stefan_Lang · Answer 2 · 2019-09-02T23:15:00

This part of the code is called an initializer list. See Constructors and member initializer lists - cppreference.com[^] for in-depth explanations.

P.S.:
A short explanation: the ':' indicates the start of an initializer list. Before the ':' is a call to a constructor, after the ':' comes a comma-separated list of member variables and the values that are used to initialize them.

For example in this case, we can see that the class CEnumContext has a member variable called m_SearchContainer, which is initialized with the value NULL.