Re: Accessing a protected member in a derived class
On 7/23/2011 7:39 AM, Johannes Schaub wrote:
Tom wrote:
Hi NG,
The following example does not compile using g++. The compiler says
"error: ???iMyVal??? was not declared in this scope" in Method MyFunction
of the derived class:
template<typename T>
class MyBase
{
protected:
int iMyVal;
};
template<typename T>
class MyDerived : public MyBase<T>
{
void MyFunction()
{
// this->iMyVal = 10;
iMyVal = 10;
}
};
int main()
{
MyDerived<int> derived;
return 0;
}
Using the line with the this-> works fine. After removing the template
stuff the code compiles also fine without this->:
"iMyVal" is an unqualified names. Unqualified name lookup won't look into
base classes whose type depends on template parameters (such as "T", or
"MyBase<T>").
If you say "this->iMyVal" or "MyDerived::iMyVal", you are using class member
access and qualified name lookup respectively. Those don't ignore dependent
base classes, and will thus find "int iMyVal;" when instantiating
"MyDerived<int>::MyFunction".
To the OP:
http://www.parashift.com/c++-faq-lite/templates.html#faq-35.19
To Johannes:
http://www.parashift.com/c++-faq-lite/how-to-post.html#faq-5.5
V
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