Questions tagged [enable-shared-from-this]
36 questions
3
votes
2 answers
How does shared_ptr detect that T derives from enable_shared_from_this?
I am trying to learn how shared_ptr works by implementing it from scratch, and I can't figure out how to detect T's base class.
I've tried using is_base_of(), but that gives a const value, which I can't use with an if statement to set the object's…
Alex
- 846
- 6
- 16
2
votes
1 answer
Question about the usage of shared_from_this() in practice
The below code snippet is seen at cppreference.
I am curious about what the intention of Best::getptr() is? When should I use this method in practice? Maybe a simple demo code helps a lot.
struct Best : std::enable_shared_from_this // note:…
John
- 2,963
- 11
- 33
2
votes
1 answer
std::enable_shared_from_this, non-virtual destructor and public inheritance
The std::enable_shared_from_this class is a (template) mixin, recommended for use to enable creating shared pointers from a given object (or its address), which all have common ownership of the object.
The thing is, that if you have an class T…
einpoklum
- 118,144
- 57
- 340
- 684
2
votes
1 answer
Bad_weak_ptr caused by call to shared_from_this with multiple inheritence
I am trying to understand why there is a bad_weak_ptr exception when calling shared_from_this.
#include
#include
class parent : public std::enable_shared_from_this
{
public:
void compare(std::shared_ptr…
PVRT
- 480
- 4
- 13
2
votes
4 answers
Why does std::enable_shared_from_this allow multiple std::shared_ptr instances?
There are several questions that cover the behavior of std::enable_shared_from_this, but I don't think that this is a duplicate.
Classes that inherit from std::enable_shared_from_this carry a std::weak_ptr member. When the application creates a…
Willis Blackburn
- 8,068
- 19
- 36
1
vote
2 answers
Initializing a member with type std::shared_ptr of a class A with a pointer to class B in a member function of B
I have the following code:
class Cohomology;
struct EMField
{
std::shared_ptr coh;
std::array data;
// other methods
}
class Cohomology
{
private:
// private members
public:
…
rungekutta
- 39
- 5
1
vote
1 answer
when to use shared_from_this()
If I want to return a shared_ptr for class A, I should use shared_from_this() feature. But I think this will work after I defined a shared_ptr for A already. So if another place wants a shared_ptr I just use the one I made. I wonder when to use…
Yacheng Liu
- 51
- 4
1
vote
1 answer
pybind11, compile fails on binding Trampolines and multiple inheritance with std::enable_shared_from_this
I have a compile problem with multiple inhertance combined with trampolines. The next code explains the problem:
#include
#include
namespace py = pybind11;
// classes
class A {
public:
virtual int fA() const =…
Naum
- 105
- 1
- 7
1
vote
2 answers
does the move constructor invalidate shared_from_this
I would like to start a thread with a class which contains non-copyable members. In order to communicate with the thread I would like to create a shared pointer from the object before I move it into the thread.
Does the move constructor invalidate…
user1396055
- 295
- 1
- 12
0
votes
0 answers
Why is the weak reference count of a std::shared_ptr not zero after std::make_shared invoked?
After executing lines 40 and 41 below, the debugger is telling me that the weak reference count for the std::shared_ptr's a and b is 2.
The ctor for Value is not storing any strong or weak references to these objects:
struct Value : public…
wcochran
- 10,089
- 6
- 61
- 69
0
votes
2 answers
'std::bad_weak_ptr' error while using shared_from_this
Note: Before posting the question, I have gone through the existing questions on std::bad_weak_error while using shared_from_this to pass the shared_ptr of the existing shared_ptr instance to another method. None of them are similar to this…
LKB
- 127
- 2
- 8
0
votes
0 answers
Signals2 disconnects slot automatically?
Code below is a test program, emulating some events processing. Full code snippets is here. There are 3 threads for event producer, for event distributor like event bus, what handles system event too, and for a certain game, what handles significant…
fenixD
- 13
- 2
0
votes
0 answers
Using shared_from_this() with derived class
When I try to run this code:
class A : public enable_shared_from_this {
public:
A() {
cout << "A::A()" << endl;
};
virtual ~A() {
cout << "A::~A()" << endl;
};
virtual void func() {
cout <<…
Benzecat
- 1
- 1
0
votes
1 answer
Why doesn’t `std::make_shared` work anymore when the class inherits class `enable_shared_from_this`?
Why doesn’t std::make_shared work anymore when the class Widget inherits class enable_shared_from_this?
Here is the code snippet:
#include
#include
#include
class Widget:public…
John
- 2,963
- 11
- 33
0
votes
2 answers
smart pointer as argument of function which uses std::function, std::bind
#include
#include
#include
template
struct Message
{
T a;
};
template
class Connection : public std::enable_shared_from_this
{
typedef std::function&)>…
Nikita Pavlenko
- 3
- 3