Cereal Demands Smart Pointers

Funny way to learn about smart pointers and start using them.

Cereal does not support serializing raw pointers - please use a smart pointer

std::unique_ptr is for a single pointer. When the pointer variable goes out of scope the object will be destroyed. You can’t copy the pointer but you can move it like so:

std::unique_ptr<int> valuePtr(new int(15));
std::unique_ptr<int> valuePtrNow(std::move(valuePtr));

The value is still accessed using the dereference operator. *valuePtrNow . Looks like you can also cast it to a bool to determine whether the pointer has an object.

static_cast<bool>(valuePtr)

shared_ptr. Reference counting pointer for sharing outside a class. When references drop to zero the object is deleted. I should change my pointers to shared pointers for the most part. weak_ptr. Holds a reference that does not take ownership of the resource. Looks like you make a weak pointer from a shared pointer. But if no other references to the resource exist, it will be deleted and your weak pointer will be useless. Before you can access the resource with a weak pointer, you need to call .lock() which returns a shared pointer which does increment the reference count. Neat.

Back to Cereal

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I was getting an error trying to Cerealize a vector of Boids. Turns out I needed to include specific header files from Cereal. Keep it in mind.

#include <cereal/types/memory.hpp>
#include <cereal/types/vector.hpp>

Also, I used CEREAL_NVP() to get better member variable names into the output file. Looks like this in JSON:

"id": 2147483658,
"data": {
  "id": 9,
  "generationIndex": 0,
  "numFoodsEaten": 0
}

Pretty sweet. Still got some more work to do to serialize the whole thing but this is great so far.