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I have two classes; Salary that is intended to hold information and calculations regarding the salary of an employee and Employee that has an object of type class Salary and some members like name and address of the employee...
What I want to do is to prevent
class Salaryfrom being instantiated and onlyclass Employeecan instantiate it. So I declared the constructors ofSalaryprivate and madeEmployeefriend ofSalary. But I get errors:
class Employee;
class Salary {
public:
private:
Salary() : revenue_{}, cost_{} {}
Salary(int x, int y) : revenue_{ x },
cost_{ y } {
}
int revenue_, cost_;
friend class Employee;
};
class Employee {
public:
std::string name_;
Salary sal;
};
int main(){
Employee emp{}; // "Salary::Salary()" is inaccessible
}
The problem raised for me if I forward declare
main:
int main(int, char*[]);
And make
mainfriend ofclass Salaryso in Salary:
class Salary {
//...
friend int main(int argc, char* argv[]);
};
Now the program compiles correctly!
*** Another thing in main if I declare an object this way:
Employee emp; // ok
Employee emp{}; // error?
c++ constructor friend-class
asked 43 mins ago
Syfu_HSyfu_H
35018
add a comment |
I have two classes; Salary that is intended to hold information and calculations regarding the salary of an employee and Employee that has an object of type class Salary and some members like name and address of the employee...
What I want to do is to prevent
class Salaryfrom being instantiated and onlyclass Employeecan instantiate it. So I declared the constructors ofSalaryprivate and madeEmployeefriend ofSalary. But I get errors:
class Employee;
class Salary {
public:
private:
Salary() : revenue_{}, cost_{} {}
Salary(int x, int y) : revenue_{ x },
cost_{ y } {
}
int revenue_, cost_;
friend class Employee;
};
class Employee {
public:
std::string name_;
Salary sal;
};
int main(){
Employee emp{}; // "Salary::Salary()" is inaccessible
}
The problem raised for me if I forward declare
main:
int main(int, char*[]);
And make
mainfriend ofclass Salaryso in Salary:
class Salary {
//...
friend int main(int argc, char* argv[]);
};
Now the program compiles correctly!
*** Another thing in main if I declare an object this way:
Employee emp; // ok
Employee emp{}; // error?
c++ constructor friend-class
asked 43 mins ago
Syfu_HSyfu_H
35018
add a comment |
I have two classes; Salary that is intended to hold information and calculations regarding the salary of an employee and Employee that has an object of type class Salary and some members like name and address of the employee...
What I want to do is to prevent
class Salaryfrom being instantiated and onlyclass Employeecan instantiate it. So I declared the constructors ofSalaryprivate and madeEmployeefriend ofSalary. But I get errors:
class Employee;
class Salary {
public:
private:
Salary() : revenue_{}, cost_{} {}
Salary(int x, int y) : revenue_{ x },
cost_{ y } {
}
int revenue_, cost_;
friend class Employee;
};
class Employee {
public:
std::string name_;
Salary sal;
};
int main(){
Employee emp{}; // "Salary::Salary()" is inaccessible
}
The problem raised for me if I forward declare
main:
int main(int, char*[]);
And make
mainfriend ofclass Salaryso in Salary:
class Salary {
//...
friend int main(int argc, char* argv[]);
};
Now the program compiles correctly!
*** Another thing in main if I declare an object this way:
Employee emp; // ok
Employee emp{}; // error?
c++ constructor friend-class
asked 43 mins ago
Syfu_HSyfu_H
35018
I have two classes; Salary that is intended to hold information and calculations regarding the salary of an employee and Employee that has an object of type class Salary and some members like name and address of the employee...
What I want to do is to prevent
class Salaryfrom being instantiated and onlyclass Employeecan instantiate it. So I declared the constructors ofSalaryprivate and madeEmployeefriend ofSalary. But I get errors:
class Employee;
class Salary {
public:
private:
Salary() : revenue_{}, cost_{} {}
Salary(int x, int y) : revenue_{ x },
cost_{ y } {
}
int revenue_, cost_;
friend class Employee;
};
class Employee {
public:
std::string name_;
Salary sal;
};
int main(){
Employee emp{}; // "Salary::Salary()" is inaccessible
}
The problem raised for me if I forward declare
main:
int main(int, char*[]);
And make
mainfriend ofclass Salaryso in Salary:
class Salary {
//...
friend int main(int argc, char* argv[]);
};
Now the program compiles correctly!
*** Another thing in main if I declare an object this way:
Employee emp; // ok
Employee emp{}; // error?
c++ constructor friend-class
c++ constructor friend-class
asked 43 mins ago
Syfu_HSyfu_H
35018
asked 43 mins ago
Syfu_HSyfu_H
35018
edited 35 mins ago
Syfu_H
asked 43 mins ago
Syfu_HSyfu_H
35018
asked 43 mins ago
Syfu_HSyfu_H
35018
asked 43 mins ago
Syfu_HSyfu_H
35018
35018
add a comment |
add a comment |
4 Answers
4
active
oldest
votes
Because you don't provide a constructor for Employee the braces in your initialization Employee emp{}; will perform an aggregate initialization, which essentially means that each member is initialized one-by-one using the default rules, in the context of main(). Since main() doesn't have access to the Salary constructor, it fails.
As others have pointed out, adding an Employee default constructor will resolve your problem:
class Employee {
public:
Employee() = default;
std::string name_;
Salary sal;
};
answered 23 mins ago
zdanzdan
22.1k34864
I'm trying on MSVS and onlyEmployee() {};allowsEmployee emp{};to compile. Clang seems to acceptEmployee() = default;, but then again, Clang seems to accept having no default constructor here.
– wally
6 mins ago
add a comment |
You have to explicitly declare the default constructor of class Employee thus you can initialize an abject via uniform initialization:
class Employee {
public:
Employee(){} // add it
std::string name_;
Salary sal;
};
int main(){
Employee emp{}; // now this should compile
}
answered 25 mins ago
Raindrop7Raindrop7
3,74531224
add a comment |
You need Employee's ctor to call the ctor of Salary. The ctor of Salary is not accessible from main.
eg:
class Employee {
public:
Employee() : sal() {}
public:
std::string name_;
Salary sal;
};
edited 15 mins ago
Pavan Manjunath
20.1k1181108
answered 35 mins ago
schuessschuess
536416
add a comment |
If you erase the "{}" after "Employee emp" in your main() function it compiles just fine (gcc 7.3.1 on Fedora 27).
answered 36 mins ago
Eric SokolowskyEric Sokolowsky
514
1
I recommend explaining why.
– user4581301
33 mins ago
Yes. Not onyl GCC but also MSVC14 also compilesEmployee emp;but why?
– Syfu_H
32 mins ago
@Syfu_H Value Initialization. And I could be mistaken here (been caught on this in the past), but the Value Initialization is being replaced by Aggregate Initialization
– user4581301
24 mins ago
add a comment |
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4 Answers
4
active
oldest
votes
4 Answers
4
active
oldest
votes
active
oldest
votes
active
oldest
votes
Because you don't provide a constructor for Employee the braces in your initialization Employee emp{}; will perform an aggregate initialization, which essentially means that each member is initialized one-by-one using the default rules, in the context of main(). Since main() doesn't have access to the Salary constructor, it fails.
As others have pointed out, adding an Employee default constructor will resolve your problem:
class Employee {
public:
Employee() = default;
std::string name_;
Salary sal;
};
answered 23 mins ago
zdanzdan
22.1k34864
I'm trying on MSVS and onlyEmployee() {};allowsEmployee emp{};to compile. Clang seems to acceptEmployee() = default;, but then again, Clang seems to accept having no default constructor here.
– wally
6 mins ago
add a comment |
Because you don't provide a constructor for Employee the braces in your initialization Employee emp{}; will perform an aggregate initialization, which essentially means that each member is initialized one-by-one using the default rules, in the context of main(). Since main() doesn't have access to the Salary constructor, it fails.
As others have pointed out, adding an Employee default constructor will resolve your problem:
class Employee {
public:
Employee() = default;
std::string name_;
Salary sal;
};
answered 23 mins ago
zdanzdan
22.1k34864
I'm trying on MSVS and onlyEmployee() {};allowsEmployee emp{};to compile. Clang seems to acceptEmployee() = default;, but then again, Clang seems to accept having no default constructor here.
– wally
6 mins ago
add a comment |
Because you don't provide a constructor for Employee the braces in your initialization Employee emp{}; will perform an aggregate initialization, which essentially means that each member is initialized one-by-one using the default rules, in the context of main(). Since main() doesn't have access to the Salary constructor, it fails.
As others have pointed out, adding an Employee default constructor will resolve your problem:
class Employee {
public:
Employee() = default;
std::string name_;
Salary sal;
};
answered 23 mins ago
zdanzdan
22.1k34864
Because you don't provide a constructor for Employee the braces in your initialization Employee emp{}; will perform an aggregate initialization, which essentially means that each member is initialized one-by-one using the default rules, in the context of main(). Since main() doesn't have access to the Salary constructor, it fails.
As others have pointed out, adding an Employee default constructor will resolve your problem:
class Employee {
public:
Employee() = default;
std::string name_;
Salary sal;
};
answered 23 mins ago
zdanzdan
22.1k34864
edited 8 mins ago
answered 23 mins ago
zdanzdan
22.1k34864
answered 23 mins ago
zdanzdan
22.1k34864
answered 23 mins ago
zdanzdan
22.1k34864
22.1k34864
I'm trying on MSVS and onlyEmployee() {};allowsEmployee emp{};to compile. Clang seems to acceptEmployee() = default;, but then again, Clang seems to accept having no default constructor here.
– wally
6 mins ago
add a comment |
I'm trying on MSVS and onlyEmployee() {};allowsEmployee emp{};to compile. Clang seems to acceptEmployee() = default;, but then again, Clang seems to accept having no default constructor here.
– wally
6 mins ago
I'm trying on MSVS and only
Employee() {}; allows Employee emp{}; to compile. Clang seems to accept Employee() = default;, but then again, Clang seems to accept having no default constructor here.– wally
6 mins ago
I'm trying on MSVS and only
Employee() {}; allows Employee emp{}; to compile. Clang seems to accept Employee() = default;, but then again, Clang seems to accept having no default constructor here.– wally
6 mins ago
add a comment |
You have to explicitly declare the default constructor of class Employee thus you can initialize an abject via uniform initialization:
class Employee {
public:
Employee(){} // add it
std::string name_;
Salary sal;
};
int main(){
Employee emp{}; // now this should compile
}
answered 25 mins ago
Raindrop7Raindrop7
3,74531224
add a comment |
You have to explicitly declare the default constructor of class Employee thus you can initialize an abject via uniform initialization:
class Employee {
public:
Employee(){} // add it
std::string name_;
Salary sal;
};
int main(){
Employee emp{}; // now this should compile
}
answered 25 mins ago
Raindrop7Raindrop7
3,74531224
add a comment |
You have to explicitly declare the default constructor of class Employee thus you can initialize an abject via uniform initialization:
class Employee {
public:
Employee(){} // add it
std::string name_;
Salary sal;
};
int main(){
Employee emp{}; // now this should compile
}
answered 25 mins ago
Raindrop7Raindrop7
3,74531224
You have to explicitly declare the default constructor of class Employee thus you can initialize an abject via uniform initialization:
class Employee {
public:
Employee(){} // add it
std::string name_;
Salary sal;
};
int main(){
Employee emp{}; // now this should compile
}
answered 25 mins ago
Raindrop7Raindrop7
3,74531224
answered 25 mins ago
Raindrop7Raindrop7
3,74531224
answered 25 mins ago
Raindrop7Raindrop7
3,74531224
answered 25 mins ago
Raindrop7Raindrop7
3,74531224
3,74531224
add a comment |
add a comment |
You need Employee's ctor to call the ctor of Salary. The ctor of Salary is not accessible from main.
eg:
class Employee {
public:
Employee() : sal() {}
public:
std::string name_;
Salary sal;
};
edited 15 mins ago
Pavan Manjunath
20.1k1181108
answered 35 mins ago
schuessschuess
536416
add a comment |
You need Employee's ctor to call the ctor of Salary. The ctor of Salary is not accessible from main.
eg:
class Employee {
public:
Employee() : sal() {}
public:
std::string name_;
Salary sal;
};
edited 15 mins ago
Pavan Manjunath
20.1k1181108
answered 35 mins ago
schuessschuess
536416
add a comment |
You need Employee's ctor to call the ctor of Salary. The ctor of Salary is not accessible from main.
eg:
class Employee {
public:
Employee() : sal() {}
public:
std::string name_;
Salary sal;
};
edited 15 mins ago
Pavan Manjunath
20.1k1181108
answered 35 mins ago
schuessschuess
536416
You need Employee's ctor to call the ctor of Salary. The ctor of Salary is not accessible from main.
eg:
class Employee {
public:
Employee() : sal() {}
public:
std::string name_;
Salary sal;
};
edited 15 mins ago
Pavan Manjunath
20.1k1181108
answered 35 mins ago
schuessschuess
536416
edited 15 mins ago
Pavan Manjunath
20.1k1181108
edited 15 mins ago
Pavan Manjunath
20.1k1181108
edited 15 mins ago
Pavan Manjunath
20.1k1181108
20.1k1181108
answered 35 mins ago
schuessschuess
536416
answered 35 mins ago
schuessschuess
536416
answered 35 mins ago
schuessschuess
536416
536416
add a comment |
add a comment |
If you erase the "{}" after "Employee emp" in your main() function it compiles just fine (gcc 7.3.1 on Fedora 27).
answered 36 mins ago
Eric SokolowskyEric Sokolowsky
514
1
I recommend explaining why.
– user4581301
33 mins ago
Yes. Not onyl GCC but also MSVC14 also compilesEmployee emp;but why?
– Syfu_H
32 mins ago
@Syfu_H Value Initialization. And I could be mistaken here (been caught on this in the past), but the Value Initialization is being replaced by Aggregate Initialization
– user4581301
24 mins ago
add a comment |
If you erase the "{}" after "Employee emp" in your main() function it compiles just fine (gcc 7.3.1 on Fedora 27).
answered 36 mins ago
Eric SokolowskyEric Sokolowsky
514
1
I recommend explaining why.
– user4581301
33 mins ago
Yes. Not onyl GCC but also MSVC14 also compilesEmployee emp;but why?
– Syfu_H
32 mins ago
@Syfu_H Value Initialization. And I could be mistaken here (been caught on this in the past), but the Value Initialization is being replaced by Aggregate Initialization
– user4581301
24 mins ago
add a comment |
If you erase the "{}" after "Employee emp" in your main() function it compiles just fine (gcc 7.3.1 on Fedora 27).
answered 36 mins ago
Eric SokolowskyEric Sokolowsky
514
If you erase the "{}" after "Employee emp" in your main() function it compiles just fine (gcc 7.3.1 on Fedora 27).
answered 36 mins ago
Eric SokolowskyEric Sokolowsky
514
answered 36 mins ago
Eric SokolowskyEric Sokolowsky
514
answered 36 mins ago
Eric SokolowskyEric Sokolowsky
514
answered 36 mins ago
Eric SokolowskyEric Sokolowsky
514
514
1
I recommend explaining why.
– user4581301
33 mins ago
Yes. Not onyl GCC but also MSVC14 also compilesEmployee emp;but why?
– Syfu_H
32 mins ago
@Syfu_H Value Initialization. And I could be mistaken here (been caught on this in the past), but the Value Initialization is being replaced by Aggregate Initialization
– user4581301
24 mins ago
add a comment |
1
I recommend explaining why.
– user4581301
33 mins ago
Yes. Not onyl GCC but also MSVC14 also compilesEmployee emp;but why?
– Syfu_H
32 mins ago
@Syfu_H Value Initialization. And I could be mistaken here (been caught on this in the past), but the Value Initialization is being replaced by Aggregate Initialization
– user4581301
24 mins ago
1
1
I recommend explaining why.
– user4581301
33 mins ago
I recommend explaining why.
– user4581301
33 mins ago
Yes. Not onyl GCC but also MSVC14 also compiles
Employee emp; but why?– Syfu_H
32 mins ago
Yes. Not onyl GCC but also MSVC14 also compiles
Employee emp; but why?– Syfu_H
32 mins ago
@Syfu_H Value Initialization. And I could be mistaken here (been caught on this in the past), but the Value Initialization is being replaced by Aggregate Initialization
– user4581301
24 mins ago
@Syfu_H Value Initialization. And I could be mistaken here (been caught on this in the past), but the Value Initialization is being replaced by Aggregate Initialization
– user4581301
24 mins ago
add a comment |
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