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Const in function prototype

I am trying to understand a piece of C ++ code and I came to the conclusion that I do not understand what the following means:

The following is indicated in the function prototype file: aka (.h)

What I'm puzzled about is the const parameter:

ofMesh getImageMesh() const;

I mean that the function / method returns the class ofMesh, getImageMesh () has no parameters, and that follows const. Why is const used like this?

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3 answers

This is a method const, which means that you can call it on objects const, and it will not change members not mutable, and it will not call other methods not const.

struct X
{
    void foo();
    int x;
    void goo() const;
};

void X::goo() const
{
   x = 3;  //illegal
   foo();  //illegal
}

//...
const X x;
x.foo();   //illegal
x.goo();   //OKAY
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, . , , .

OK:

class Foo
{
   int m_foo;
   int GetFoo() const
   {
       return m_foo;
   }
}

:

class Foo
{
   int m_foo;
   int GetFoo() const
   {
       m_foo += 1;
       return m_foo;
   }
}

, - , - "const correctness".

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const , . , .

That way, if you declare a member function const, you tell the compiler that the function can be called on the const object. A member function that is not specifically declared const, is seen as the one that will change the data elements in the object, and the compiler will not allow you to bring it to an object const.

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