CODEWITHSUNDEEP
c++boostshared-ptr
KaiserJohaan
KaiserJohaan

Reputation: 9240

Replacing the content of the shared pointer?

I have a shared pointer that I have shared around the system. Later on, I want to replace the actual content of these shared pointers point to, but still keep all the shared pointers valid, so they internally point to this new object.

Is there an easy way to do this with shared pointers?

Kind of like this I am looking for - pseudo-code

typedef boost::shared_ptr<Model> ModelPtr

ModelPtr model1 = ModelPtr(new Model);
ModelPtr model2 = model1;

// make something like 'model1.get() = new Model' so model1, model2 both points to a new model

EDIT: I want the effect of this, but less gimicky

ModelPtr model1 = ModelPtr(new Model("monkey"));
memcpy(model1 .get(), new Model("donkey"), sizeof(Model));

Upvotes: 16

Views: 18177

Answers (3)

W.Perrin
W.Perrin

Reputation: 4695

shared_ptr<char> p(new  char[256],std::default_delete<char[]>());
p.get()[0]='a';

memcpy do the job roughly. You may try to use reset method, but only affect the caller object.

Upvotes: 1

Mark B
Mark B

Reputation: 96241

Each shared_ptr instance has its own copy of the pointer, so there's no way for any one shared_ptr instance to know and affect the pointers of the other reference-counted shared_ptr instances.

Do you instead just want model2 to be a reference to model1 so that when you reset model1, model2 comes along with the change?

Otherwise can you elaborate further on the real problem you're trying to solve?

Upvotes: 1

awesoon
awesoon

Reputation: 33671

If I understood you correctly - you could use overloaded dereference operator:

auto a = std::make_shared<int>(42);
auto b = a;
*a = 43;

std::cout << *b << std::endl;

Output:

43

Upvotes: 14

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