How to add handler to the format function of CString

Question

First I have a CString(MFC)

CString csSQL

When format a sql string, for example

csSQL.Format( szFormat, szTableName, szColumn, szValue, intValue )

I need to handle the special char in szValue, so I need write a new class MySQLString

mySQLcs.FormatSQL( szFormat, szTableName, szColumn, szValue, intValue )

which has the functionality

csSQL.Format( szFormat, szTableName, szColumn, HandleSpecialChar(szValue), intValue )

But because the parameter The format function accept is not fixed. I found it difficult. Is there any solution?

Answer 1

You don't add a handler to the CString class.

You write a (new) function

CString FormatSQLString(CString const& format, CString const& tableName, CString const& columnName, CString const& value) {
  CString csSQL;
  return csSQL.Format(format, tableName, columnName, HandleSpecialChar(value));
}

and you wrap that function further up (e.g. CString GetUpdateStmt(tableName, columnName, value)) so that you don't have to sprinkle format strings all over your code.

When you write code where you use the input for an SQL statement in a structured way, be that as with a collection of functions such as I proposed, be that by using or creating a SQLQueryStringBuilder (made up name) class, then you won't have the problem of having to shoehorn something into the string formatting that doesn't belong there.