Not getting the expected behavior with "explicit" keyword in c++

Question

I have the following classes

class abc
{
private:
  string name_;
public:
  explicit abc(string name);
};

class xyz
{
private:
  abc obj_abc_;
public:
  xyz ():obj_abc_("NOTHING") { }; //I think this should give an error since explicit is used.
};

According to what i have understood about explicit, i should be getting a compiler error whenever xyz constructor is being called; because i am initializing the obj_abc by simply assigning it to a string. But i am not getting any compiler error here. What am i missing?

explicit abc(string name):name_(name); This compiled?

PaulMcKenzie
– PaulMcKenzie

2014-12-12 15:58:31 +00:00
Commented Dec 12, 2014 at 15:58 — PaulMcKenzie
– PaulMcKenzie, Commented Dec 12, 2014 at 15:58

Mike Seymour · Accepted Answer · 2014-12-12 16:09:32Z

2

explicit on a constructor means that the constructor can't be used for conversion from its parameter type to the class type. So an implicit conversion

abc x = "NOTHING";

will be forbidden if the constructor is explicit, but not otherwise. An explicit conversion

abc x("NOTHING");

will be allowed in either case. In your case, direct initialisation in an initialiser list is explicit; so your explicit constructor can be used for that.

explicit doesn't prevent implicit conversions to the constructor parameter's type; so the conversion from "NOTHING" to string in your example is allowed in either case, using the non-explicit string constructor.

answered Dec 12, 2014 at 16:09

Mike Seymour

256k30 gold badges467 silver badges658 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

user1804599 · Accepted Answer · 2014-12-12 15:57:53Z

0

Besides the syntax error (use { } instead of ;) you aren't assigning or implicitly converting anything. You're explicitly constructing the object in the initialisation list.

answered Dec 12, 2014 at 15:57

user1804599

Collectives™ on Stack Overflow

Not getting the expected behavior with "explicit" keyword in c++

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related