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From:Maarten Schrijvers Date:October 2 2007 3:00pm
Subject:Null values do not compile...
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I have some fields which can be (SQL) NULL. If they are filled they are
varchar, but they're not necessary, so they could be NULL.
Compiling gives me an error though:

c:\mysql++\include\null.h(206) : error C2593: 'operator =' is ambiguous

1> E:\Program Files\Microsoft Visual Studio 8\VC\include\xstring(923): could
be 'std::basic_string<_Elem,_Traits,_Ax>
&std::basic_string<_Elem,_Traits,_Ax>::operator =(_Elem)'

1> with

1> [

1> _Elem=char,

1> _Traits=std::char_traits<char>,

1> _Ax=std::allocator<char>

1> ]

1> E:\Program Files\Microsoft Visual Studio 8\VC\include\xstring(918): or
'std::basic_string<_Elem,_Traits,_Ax>
&std::basic_string<_Elem,_Traits,_Ax>::operator =(const _Elem *)'

1> with

1> [

1> _Elem=char,

1> _Traits=std::char_traits<char>,

1> _Ax=std::allocator<char>

1> ]

1> E:\Program Files\Microsoft Visual Studio 8\VC\include\xstring(913): or
'std::basic_string<_Elem,_Traits,_Ax>
&std::basic_string<_Elem,_Traits,_Ax>::operator =(const
std::basic_string<_Elem,_Traits,_Ax> &)'

1> with

1> [

1> _Elem=char,

1> _Traits=std::char_traits<char>,

1> _Ax=std::allocator<char>

1> ]

1> while trying to match the argument list '(mysqlpp::sql_varchar,
mysqlpp::null_type)'

1> c:\mysql++\include\null.h(204) : while compiling class template member
function 'mysqlpp::Null<Type>::operator Type(void)'

1> with

1> [

1> Type=mysqlpp::sql_varchar

1> ]

1> e:\visual studio 2005\projects\t_1\urenregistratie\Relatieonderhoud.h(25)
: see reference to class template instantiation 'mysqlpp::Null<Type>' being
compiled

1> with

1> [

1> Type=mysqlpp::sql_varchar

1> ]

I have declared the following:

typedef mysqlpp::Null<mysqlpp::sql_varchar> Nullstr;

static Nullstr vVoornamen = mysqlpp::null; //gave the variable a value
trying to avoid the error

What am I doing wrong?

Thread
Null values do not compile...Maarten Schrijvers2 Oct
  • Re: Null values do not compile...Maarten Schrijvers3 Oct