09-weak_ptr.cpp
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#include <assert.h>
#include <iostream>
#include <memory>
class Example {
public:
int val;
Example() : val(0)
{
std::cout << "Example::Example()" << std::endl;
}
Example(int a) : val(a)
{
std::cout << "Example::Example(" << a << ")" << std::endl;
}
~Example()
{
std::cout << "Example::~Example()" << std::endl;
}
};
int main()
{
std::weak_ptr<Example> w1;
{
std::shared_ptr<Example> p1 = std::make_shared<Example>();
w1 = p1;
std::shared_ptr<Example> p2 = w1.lock();
assert(p2 != nullptr);
}
std::shared_ptr<Example> p3 = w1.lock();
assert(p3 == nullptr);
}