Question

First of all, the code:

template<typename Func, typename Func2>
void ForEachField(Func normalHandler, Func2 arrayHandler = NULL, bool skipUnknowns = true)
{
    for(int i = 0; i < mFields.size(); ++i)
    {
        Field *f = mFields[i];

        if(skipUnknowns && f->IsUnknown())
            continue;

        if(f->GetCount() == 1 || !arrayHandler)
            normalHandler(f);
        else
            arrayHandler(f);
    }
}

And an example of usage:

df->ForEachField(
    [&](Field *field) { f << "\t" << format("public $%s;\n") % field->GetName(); },
    [&](Field *field) { f << "\t" << format("public $%s;\n") % field->GetName() % field->GetSize(); }
); // Works

df->ForEachField(
    [&](Field *field) { WriteLine(f, format("\t\t'%s' => array('type' => '%s'),") % field->GetName() % field->GetTypeInfo()->Name);
}); // Doesn't work

The second call doesn’t work because it says:

OutputPhp.cpp(27): error C2783: ‘void
DataFile::ForEachField(Func,Func2,bool)’
: could not deduce template argument
for ‘Func2’
see declaration of ‘DataFile::ForEachField’

Is there any way I can make the second parameter optional, while still using templates, and while not having to manually specify the second template argument?

Answer 1

You could add an overload for ForEachField:

template<typename Func>
void ForEachField (Func normalHandler)
{
    ForEachField<Func, void *>(normalHandler, NULL, true);
}