Question on constructors in Inheritance

[yungman]

But it's not in a function.

Think about it this way - when do you expect it to run?

Ah! I have to try to execute the line, the line is just sitting there!

I'll be back. Thanks so much.

 

[yungman]

Thank you, it works. Never thought of this! That the line needs to be called, too used to just cout in main().

Thanks

 

[Mark44]

I have a strange error I cannot explain.

#include<iostream>
using std::cout;
class Bclass  //members = a, b, fun0 and fun1
   {public: int a = 2, b = 3;
    void fun0() { cout << " Bclass fun0()." << "\n\n";}
    void fun1() { cout << " Bclass fun1()." << "\n\n";}};
class Dclass : public Bclass//members = a, fun1 and fun2
{public: int a = 5;//This overrides a in Bclass.
    cout << " Dclass.a = " << a << ", Bclass.a = " << Bclass.a << "\n\n";
    void fun1() { Bclass::fun1(); }//use fun1 in Bclass
    void fun2() { cout << " Dclass fun2()." << "\n\n";} };
int main()
   {Dclass DC2; DC2.fun0(); DC2.fun1(); DC2.fun2();
    cout << " DC2.a= " << DC2.a << ", DC2.b= " << DC2.b << "\n\n";
}//a in Dclass overrides a in Bclass, DC2.a=5. b inherits from Bclass.

If you didn't cram all your code so tightly, it might have been more obvious that you have an executable statement (the output line) in amongst the declarations of the Dclass members. It's a false economy to jam everything together like you often seem to do.

 

[yungman]

If you didn't cram all your code so tightly, it might have been more obvious that you have an executable statement (the output line) in amongst the declarations of the Dclass members. It's a false economy to jam everything together like you often seem to do.

It's one line of code per line. It's not tight without the comments.

 

[Vanadium 50]

It's one line of code per line.

That is tautologically true. It also misses the point: most people would write

void fun1() { cout << " Bclass fun1()." << "\n\n";}};

as either 4 or 5 lines.

Mark told you many times that this is good practice.
You have not done this - even after running into problems doing it "your way". Repeatedly.
Why is that? Do you think you're smarter than Mark? Do you think you're a better programmer? Is it because you know that if you get into trouble we will bail you out again and again and again?

 

[yungman]

Your attempt to call cout is not inside any function definition. This is not allowed. Did you mean to do it inside the Dclass constructor? If so, you have to define a Dclass constructor!

Sorry I did not see your post till now.

Thanks

 

[Mark44]

Here's the same code you posted, minus the comments. It's still tight

#include<iostream>
using std::cout;
class Bclass
   {public: int a = 2, b = 3;
    void fun0() { cout << " Bclass fun0()." << "\n\n";}
    void fun1() { cout << " Bclass fun1()." << "\n\n";}};
class Dclass : public Bclass
{public: int a = 5;
    cout << " Dclass.a = " << a << ", Bclass.a = " << Bclass.a << "\n\n";
    void fun1() { Bclass::fun1(); }
    void fun2() { cout << " Dclass fun2()." << "\n\n";} };
int main()
   {Dclass DC2; DC2.fun0(); DC2.fun1(); DC2.fun2();
    cout << " DC2.a= " << DC2.a << ", DC2.b= " << DC2.b << "\n\n";
}

When you wrote "It's one line of code per line." you probably meant one instruction per line, but in main() you have a declaration and three function calls all on one line.

Here's the same code as above, but spaced out to increase readability.

#include<iostream>
using std::cout;

class Bclass
{
public:
    int a = 2, b = 3;
    void fun0() { cout << " Bclass fun0()." << "\n\n";}
    void fun1() { cout << " Bclass fun1()." << "\n\n";}
};

class Dclass : public Bclass
{
public:
    int a = 5;
    cout << " Dclass.a = " << a << ", Bclass.a = " << Bclass.a << "\n\n";
    void fun1() { Bclass::fun1(); }
    void fun2() { cout << " Dclass fun2()." << "\n\n";}
};

int main()
{
    Dclass DC2;
    DC2.fun0();
    DC2.fun1();
    DC2.fun2();
    cout << " DC2.a= " << DC2.a << ", DC2.b= " << DC2.b << "\n\n";
}

With a reasonable amount of whitespace, it's much more obvious that in the declaration section of Dclass, you have an executable statement (cout << ...) mixed in with the declarations.