in C++ is it a bad practice to use reference in place of getters?
for example:
class X { int mP; public: const int& P; X():P(mP){} }; and later
X xl; int h = xl.P; 
2 Answers
Just think about refactoring to make the access thread safe, that won't work well this way and require a lot of changes in the client classes/functions.
If you have class members, that are guaranteed not to be changed over lifetime of the instance, you can simply provide const int P; and initialize it properly in your class' constructors.
If the value is to be visible class wide use a static const int P;
In any other case use a public getter:
int P() const; // a return type of 'const int &' would be redundant 1st shot implementation:
int X::P() const { return mP; } Thread safe implementation:
class X { { // ... private: // ... mutable std::mutex internalDataGuard; }; int X::P() const { std::lock(internalDataGuard); return mP; } 1 Comment
πάντα ῥεῖ
@user2173884 Depend's on your use case. But if you abstract it out in your designs early (as you don't do with
public const int& P;), will make it easier to scale out later. I think I have explained the exceptional cases well.None of this is good:
class X { public: int x; }; class X { private: int m_x; public: const int& get() const { return m_x; } public: void set(const int& other) { m_x = other; } }; class X { private: int m_x; public: const int& x() const { return m_x; } public: void x(const int& other) { m_x = other; } }; class X { private: int m_x; public: const int& x() const { return m_x; } public: int& x() { return m_x; } }; Pick one, it's a design decision.
Having 'const int& x' to publish the private member will work:
class X { private: int m_x; public: const int& x; public: X() : m_x(0), x(m_x) {} // Take care for copy and assignment }; The cost is a larger memory footprint.
5 Comments
Shubham
How would this cost larger memory footprint?
Shubham
I guess Reference do not take any memory. they are resolved during compile time, they are just an alias in variable table created by compiler which does not exist after linking.
Shubham
Indeed. I just checked it actually take pointer size. Valid point to not to use this.
mPpublic?