How to overload both directions of an assignment operator in C++?

Question

I have a weird union I am using for alignment reasons.

I have overloaded it so that it can be assigned a string value.

Now I wish to overload the = operator so that I can assign it TO a string value.

union Tag { std::string * path; long id; }; struct TextureID { Tag ID; int type; TextureID& operator= (std::string str){ ID.path = new std::string(str); type=0; } TextureID& operator= (long val){ ID.id = val; type=1; } };

In this case we have overloaded the operators such that

TextureID t = "hello";

Is a valid statement.

How may I overwrite the = operator to be able to do:

string s = t;

Sounds like an XY problem - I cannot believe there is any reason for attempting to do this. — user2100815
– user2100815, Commented Jul 13, 2018 at 22:46
Is this Q&A any help? How do conversion operators work in C++? — user4581301
– user4581301, Commented Jul 13, 2018 at 22:47
Also if you compiler is up to date with the C++17 standard you should take a look at std::variant. — user4581301
– user4581301, Commented Jul 13, 2018 at 22:48
@NeilButterworth How is this an XY problem? All I want is to be able to assign to a string the value stored in the union. Seems pretty simple conceptually. — Makogan
– Makogan, Commented Jul 13, 2018 at 22:49
1201ProgramAlarm's posted as good an answer for the actual question as I think you can get, and the comments are wandering off topic for Stack Overflow. Once you have this all sorted out and working, I recommend making a little sample program demonstrating TextureID and how you use it and post over at Code Review to see what improvements/alternatives are out there. — user4581301
– user4581301, Commented Jul 13, 2018 at 23:30

1201ProgramAlarm · Accepted Answer · 2018-07-13 23:00:47Z

You can create a conversion operator to convert your TextureID to a std::string

operator std::string() const { // logic to create a string to return }

or create an explicit function to do the conversion

std::string to_string() const { // logic to create a string to return }

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