Thread: trouble with const correctnes

Hello all,

i use the following functions in a class:

Code:

// .h
...
private:
string* machineId;
...
public:
const string* const getId() const {return machineId;}
const string* getDebugString();
...

// .cpp
...
const string* Machine::getDebugString()
{
	stringstream ss;
	ss << "    <machine>  id= " << *machineId << "  start state= " 
		<< *( getStateFromStateId(startStateId)->getId() ) << "\n"; // *ERROR*
	for (vector<State*>::const_iterator i = stateVector.begin(); i != stateVector.end(); ++i)
	{
		ss << *( (**i).getDebugString() );
	}
	ss << "    </machine>\n";
	return new string( ss.str() );
}
...

The errormessage is:

./src/Machine.cpp: In member function 'const std::string* Machine::getDebugString()':
../src/Machine.cpp:23: error: passing 'const State' as 'this' argument of 'const std::string* State::getId()' discards qualifiers
make: *** [src/Machine.o] Error 1

Could someone please tell me what i'm doing wrong?
I tried to apply const-correctness to my program. I guarantee the "getId() const" does not mutate anything in my object to the compiler but he still complains.

thank you in advance!

Hi mario,

from same .h file:

Code:

const State* getStateFromStateId(string* sId) const;

does this help?

Originally Posted by Mario F.

It didn't actually. My initial statement makes little sense anyways. Just too tired today.

Please take a good look at the error message again... look at the prototype specified for stateID()



There is no const there declaring the function as const.

Thank you, but I think I didn't get the message :-(
in my initial post there is

Code:

// .h
...
private:
string* machineId;
...
public:
const string* const getId() const {return machineId;}  // <--prototype with const
const string* getDebugString();
...

so why do you say thte getId() method isn't const?

That is from the Machine class, right? Mario F. is referring to the State class's getId() function.

sorry sorry sorry, you are completely right.
It seems you know my code better than me, I better go hiding myself somethere