passing const char* to the string&

[ragged_hippy]

Hi,

If I have a method that has string reference as a parameter, what
happens if I pass a const char* variable to this method?

One thought is that a temporary string will be created in the stack
and the parameter will refer to this object. Is this correct?

Does this mean if a constructor of a class has a string reference
parameter, the temporary string that is created in the stack is
destroyed after the contruction of the object is complete?

** Example**
e.g:
class x {
public:
x(std::string& name);
};

void main()
{
const char* const text = "Name";
x newObject(name);
}

Can anyone help me understand what happens during and after the
newObject is created?

Thanks,
-PJ.

 

[Gianni Mariani]

Hi,

If I have a method that has string reference as a parameter, what
happens if I pass a const char* variable to this method?

One thought is that a temporary string will be created in the stack
and the parameter will refer to this object. Is this correct?

Yes, a temporary std::string is created.

Does this mean if a constructor of a class has a string reference
parameter, the temporary string that is created in the stack is
destroyed after the contruction of the object is complete?

** Example**
e.g:
class x {
public:
x(std::string& name);

Must be a "const std::string&"

x( const std::string & name );

};

void main()
{
const char* const text = "Name";
x newObject(name);
}

Can anyone help me understand what happens during and after the
newObject is created?

It would do somthing similar to this:-

void main()
{
const char* const text = "Name";


{
const std::string temp( text );
x newObject( temp );
// temp destructs just before leaving
}

}

 

[Rolf Magnus]

Hi,

If I have a method that has string reference as a parameter, what
happens if I pass a const char* variable to this method?
Depends.

One thought is that a temporary string will be created in the stack
and the parameter will refer to this object. Is this correct?

If the reference refers to a const std::string, yes. Otherwise, you should
get a compile error, because binding a non-const reference to a temporary
is forbidden.

Does this mean if a constructor of a class has a string reference
parameter, the temporary string that is created in the stack is
destroyed after the contruction of the object is complete?
Yes.

** Example**
e.g:
class x {
public:
x(std::string& name);

Change that to:

x(const std::string& name);

};

void main()

Change that to:

int main()

{
const char* const text = "Name";
x newObject(name);
}

Can anyone help me understand what happens during and after the
newObject is created?

Well, before newObject is created, a temporary std::string is created and
filled with "Name". This string lives while the constructor of newObject is
running and is destroyed immediately afterwards.