Set callback function using unique_ptr of another class
0
I am in need to implement a callback method using a unique_ptr of another class:
#include <iostream>
#include <functional>
#include <memory>
class A
{
public:
void Show(void) {}
};
class B
{
public:
void SetCB(std::function<void(void)> callb);
private:
std::function<void(void)> cb;
};
void B::SetCB(std::function<void(void)> callb)
{
cb= callb;
}
int main()
{
std::unique_ptr<A> a1 = std::make_unique<A>();
std::unique_ptr<B> b1 = std::make_unique<B>();
b1->SetCB(&a1->Show, a1.get());
}
I am getting compilation error:
$ c++ -std=c++14 try68.cpp
try68.cpp: In function 'int main()':
try68.cpp:28:29: error: no matching function for call to 'B::SetCB(<unresolved overloaded function type>, std::unique_ptr<A>::pointer)'
b1->SetCB(a1->Show, a1.get());
^
try68.cpp:28:29: note: candidate is:
try68.cpp:19:6: note: void B::SetCB(std::function<void()>)
void B::SetCB(std::function<void(void)> callb)
^
try68.cpp:19:6: note: candidate expects 1 argument, 2 provided
^
Is it not possible to set a callback methods using unique_ptr?
c++ c++11
asked Nov 25 '18 at 15:13
ProgrammerProgrammer
3,0341852105
add a comment |
0
I am in need to implement a callback method using a unique_ptr of another class:
#include <iostream>
#include <functional>
#include <memory>
class A
{
public:
void Show(void) {}
};
class B
{
public:
void SetCB(std::function<void(void)> callb);
private:
std::function<void(void)> cb;
};
void B::SetCB(std::function<void(void)> callb)
{
cb= callb;
}
int main()
{
std::unique_ptr<A> a1 = std::make_unique<A>();
std::unique_ptr<B> b1 = std::make_unique<B>();
b1->SetCB(&a1->Show, a1.get());
}
I am getting compilation error:
$ c++ -std=c++14 try68.cpp
try68.cpp: In function 'int main()':
try68.cpp:28:29: error: no matching function for call to 'B::SetCB(<unresolved overloaded function type>, std::unique_ptr<A>::pointer)'
b1->SetCB(a1->Show, a1.get());
^
try68.cpp:28:29: note: candidate is:
try68.cpp:19:6: note: void B::SetCB(std::function<void()>)
void B::SetCB(std::function<void(void)> callb)
^
try68.cpp:19:6: note: candidate expects 1 argument, 2 provided
^
Is it not possible to set a callback methods using unique_ptr?
c++ c++11
asked Nov 25 '18 at 15:13
ProgrammerProgrammer
3,0341852105
add a comment |
0
0
0
I am in need to implement a callback method using a unique_ptr of another class:
#include <iostream>
#include <functional>
#include <memory>
class A
{
public:
void Show(void) {}
};
class B
{
public:
void SetCB(std::function<void(void)> callb);
private:
std::function<void(void)> cb;
};
void B::SetCB(std::function<void(void)> callb)
{
cb= callb;
}
int main()
{
std::unique_ptr<A> a1 = std::make_unique<A>();
std::unique_ptr<B> b1 = std::make_unique<B>();
b1->SetCB(&a1->Show, a1.get());
}
I am getting compilation error:
$ c++ -std=c++14 try68.cpp
try68.cpp: In function 'int main()':
try68.cpp:28:29: error: no matching function for call to 'B::SetCB(<unresolved overloaded function type>, std::unique_ptr<A>::pointer)'
b1->SetCB(a1->Show, a1.get());
^
try68.cpp:28:29: note: candidate is:
try68.cpp:19:6: note: void B::SetCB(std::function<void()>)
void B::SetCB(std::function<void(void)> callb)
^
try68.cpp:19:6: note: candidate expects 1 argument, 2 provided
^
Is it not possible to set a callback methods using unique_ptr?
c++ c++11
asked Nov 25 '18 at 15:13
ProgrammerProgrammer
3,0341852105
I am in need to implement a callback method using a unique_ptr of another class:
#include <iostream>
#include <functional>
#include <memory>
class A
{
public:
void Show(void) {}
};
class B
{
public:
void SetCB(std::function<void(void)> callb);
private:
std::function<void(void)> cb;
};
void B::SetCB(std::function<void(void)> callb)
{
cb= callb;
}
int main()
{
std::unique_ptr<A> a1 = std::make_unique<A>();
std::unique_ptr<B> b1 = std::make_unique<B>();
b1->SetCB(&a1->Show, a1.get());
}
I am getting compilation error:
$ c++ -std=c++14 try68.cpp
try68.cpp: In function 'int main()':
try68.cpp:28:29: error: no matching function for call to 'B::SetCB(<unresolved overloaded function type>, std::unique_ptr<A>::pointer)'
b1->SetCB(a1->Show, a1.get());
^
try68.cpp:28:29: note: candidate is:
try68.cpp:19:6: note: void B::SetCB(std::function<void()>)
void B::SetCB(std::function<void(void)> callb)
^
try68.cpp:19:6: note: candidate expects 1 argument, 2 provided
^
Is it not possible to set a callback methods using unique_ptr?
c++ c++11
c++ c++11
asked Nov 25 '18 at 15:13
ProgrammerProgrammer
3,0341852105
asked Nov 25 '18 at 15:13
ProgrammerProgrammer
3,0341852105
edited Nov 25 '18 at 15:16
Programmer
asked Nov 25 '18 at 15:13
ProgrammerProgrammer
3,0341852105
asked Nov 25 '18 at 15:13
ProgrammerProgrammer
3,0341852105
asked Nov 25 '18 at 15:13
ProgrammerProgrammer
3,0341852105
3,0341852105
add a comment |
add a comment |
1 Answer
1
active
oldest
votes
1
Use a lambda, it will work like a charm:
b1->SetCB([&](){a1->Show();});
You may want to move the callback as well:
void B::SetCB(std::function<void(void)> callb)
{
cb = std::move(callb);
}
answered Nov 25 '18 at 15:14
Matthieu BrucherMatthieu Brucher
16.6k32143
Thanks - please explain that do we need to move the callback as well as you have stated "may want to move" - why?
– Programmer
Nov 25 '18 at 15:23
You don't have to move it, but if you have a callback more complex, with states and other things, there is no need to copy it when you can simply move it at a lower cost.
– Matthieu Brucher
Nov 25 '18 at 15:27
Just a another questions what if we have arguments to be passed using std::placeholders ?
– Programmer
Nov 25 '18 at 15:32
2
Themovewon't actually save anything if the states are not sophisticated. For example, moving a pointer or an int or a float won't do anything special. But for more complex states, like a string or a vector, then a move is of potential benefit.
– Eljay
Nov 25 '18 at 15:35
I think @Eljay summed it well!
– Matthieu Brucher
Nov 25 '18 at 15:37
add a comment |
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1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
1
Use a lambda, it will work like a charm:
b1->SetCB([&](){a1->Show();});
You may want to move the callback as well:
void B::SetCB(std::function<void(void)> callb)
{
cb = std::move(callb);
}
answered Nov 25 '18 at 15:14
Matthieu BrucherMatthieu Brucher
16.6k32143
Thanks - please explain that do we need to move the callback as well as you have stated "may want to move" - why?
– Programmer
Nov 25 '18 at 15:23
You don't have to move it, but if you have a callback more complex, with states and other things, there is no need to copy it when you can simply move it at a lower cost.
– Matthieu Brucher
Nov 25 '18 at 15:27
Just a another questions what if we have arguments to be passed using std::placeholders ?
– Programmer
Nov 25 '18 at 15:32
2
Themovewon't actually save anything if the states are not sophisticated. For example, moving a pointer or an int or a float won't do anything special. But for more complex states, like a string or a vector, then a move is of potential benefit.
– Eljay
Nov 25 '18 at 15:35
I think @Eljay summed it well!
– Matthieu Brucher
Nov 25 '18 at 15:37
add a comment |
1
Use a lambda, it will work like a charm:
b1->SetCB([&](){a1->Show();});
You may want to move the callback as well:
void B::SetCB(std::function<void(void)> callb)
{
cb = std::move(callb);
}
answered Nov 25 '18 at 15:14
Matthieu BrucherMatthieu Brucher
16.6k32143
Thanks - please explain that do we need to move the callback as well as you have stated "may want to move" - why?
– Programmer
Nov 25 '18 at 15:23
You don't have to move it, but if you have a callback more complex, with states and other things, there is no need to copy it when you can simply move it at a lower cost.
– Matthieu Brucher
Nov 25 '18 at 15:27
Just a another questions what if we have arguments to be passed using std::placeholders ?
– Programmer
Nov 25 '18 at 15:32
2
Themovewon't actually save anything if the states are not sophisticated. For example, moving a pointer or an int or a float won't do anything special. But for more complex states, like a string or a vector, then a move is of potential benefit.
– Eljay
Nov 25 '18 at 15:35
I think @Eljay summed it well!
– Matthieu Brucher
Nov 25 '18 at 15:37
add a comment |
1
1
1
Use a lambda, it will work like a charm:
b1->SetCB([&](){a1->Show();});
You may want to move the callback as well:
void B::SetCB(std::function<void(void)> callb)
{
cb = std::move(callb);
}
answered Nov 25 '18 at 15:14
Matthieu BrucherMatthieu Brucher
16.6k32143
Use a lambda, it will work like a charm:
b1->SetCB([&](){a1->Show();});
You may want to move the callback as well:
void B::SetCB(std::function<void(void)> callb)
{
cb = std::move(callb);
}
answered Nov 25 '18 at 15:14
Matthieu BrucherMatthieu Brucher
16.6k32143
answered Nov 25 '18 at 15:14
Matthieu BrucherMatthieu Brucher
16.6k32143
answered Nov 25 '18 at 15:14
Matthieu BrucherMatthieu Brucher
16.6k32143
answered Nov 25 '18 at 15:14
Matthieu BrucherMatthieu Brucher
16.6k32143
16.6k32143
Thanks - please explain that do we need to move the callback as well as you have stated "may want to move" - why?
– Programmer
Nov 25 '18 at 15:23
You don't have to move it, but if you have a callback more complex, with states and other things, there is no need to copy it when you can simply move it at a lower cost.
– Matthieu Brucher
Nov 25 '18 at 15:27
Just a another questions what if we have arguments to be passed using std::placeholders ?
– Programmer
Nov 25 '18 at 15:32
2
Themovewon't actually save anything if the states are not sophisticated. For example, moving a pointer or an int or a float won't do anything special. But for more complex states, like a string or a vector, then a move is of potential benefit.
– Eljay
Nov 25 '18 at 15:35
I think @Eljay summed it well!
– Matthieu Brucher
Nov 25 '18 at 15:37
add a comment |
Thanks - please explain that do we need to move the callback as well as you have stated "may want to move" - why?
– Programmer
Nov 25 '18 at 15:23
You don't have to move it, but if you have a callback more complex, with states and other things, there is no need to copy it when you can simply move it at a lower cost.
– Matthieu Brucher
Nov 25 '18 at 15:27
Just a another questions what if we have arguments to be passed using std::placeholders ?
– Programmer
Nov 25 '18 at 15:32
2
Themovewon't actually save anything if the states are not sophisticated. For example, moving a pointer or an int or a float won't do anything special. But for more complex states, like a string or a vector, then a move is of potential benefit.
– Eljay
Nov 25 '18 at 15:35
I think @Eljay summed it well!
– Matthieu Brucher
Nov 25 '18 at 15:37
Thanks - please explain that do we need to move the callback as well as you have stated "may want to move" - why?
– Programmer
Nov 25 '18 at 15:23
Thanks - please explain that do we need to move the callback as well as you have stated "may want to move" - why?
– Programmer
Nov 25 '18 at 15:23
You don't have to move it, but if you have a callback more complex, with states and other things, there is no need to copy it when you can simply move it at a lower cost.
– Matthieu Brucher
Nov 25 '18 at 15:27
You don't have to move it, but if you have a callback more complex, with states and other things, there is no need to copy it when you can simply move it at a lower cost.
– Matthieu Brucher
Nov 25 '18 at 15:27
Just a another questions what if we have arguments to be passed using std::placeholders ?
– Programmer
Nov 25 '18 at 15:32
Just a another questions what if we have arguments to be passed using std::placeholders ?
– Programmer
Nov 25 '18 at 15:32
2
2
The
move won't actually save anything if the states are not sophisticated. For example, moving a pointer or an int or a float won't do anything special. But for more complex states, like a string or a vector, then a move is of potential benefit.– Eljay
Nov 25 '18 at 15:35
The
move won't actually save anything if the states are not sophisticated. For example, moving a pointer or an int or a float won't do anything special. But for more complex states, like a string or a vector, then a move is of potential benefit.– Eljay
Nov 25 '18 at 15:35
I think @Eljay summed it well!
– Matthieu Brucher
Nov 25 '18 at 15:37
I think @Eljay summed it well!
– Matthieu Brucher
Nov 25 '18 at 15:37
add a comment |
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