Let's say I have to read some configuration files to set fields of a structure. As soon as thie file has been read and the structure initialized, its fields values should not be changed.
I read many times it was bad to have structures with const fields. But then, how to make sure its fields are not changed ?
Let's come back to the case described above. I have a function supposed to read a file given as argument and instantiate the structure with the values coming from the file. Ideally, this function would return this structure by value. But if I do so with non constant fields, the client can change the values.
A solution would be to have a class to wrap the file reader, with a non const member to the read structure, and a const accessor to read the structure and its fields. But it not very satisfying.
Is there an idiom for this situation?
As @NathanOliver commented, you can make all the parameters private members, and expose public getters (and no setters).
Something like:
#include <string>
class Config {
public:
int GetP1() const { return m_p1; }
float GetP2() const { return m_p2; }
bool LoadFromFile(std::string const& filename) {
// populate m_p1, m_p2 etc.
return true;
}
private:
int m_p1{};
float m_p2{};
};
Note that there is also a public method to initialize the configuration from the file.