How to set a maximum size for my container Deque with C ++?

Question

I need help defining a maximum size of my STD container of type Deque.

Deque Documentation C++

In this case, I would have to store a maximum number of clients in a given child in a data structure as in the example below:

typedef struct Cart {
     int id;
     string clientName;
     int numberOfProducts;
     double purchaseValue;
} Cart;

I defined a constant:

#define MAX_CLIENT 10

And I'm about to define the queues, which must have a maximum of 10 clients:

deque<Cart> BOX_1(MAX_CLIENT);
deque<Cart> BOX_2(MAX_CLIENT);
deque<Cart> BOX_3(MAX_CLIENT);

But it seems that the structure is still dynamic, even defining the maximum number.

Thanks for the contribution.

Answer 1

I'm about to define the queues, which must have a maximum of 10 clients:

deque<Cart> BOX_1(MAX_CLIENT);

To clarify, that creates a deque that contains 10 carts initially.

How to set a maximum size for my container Deque with C ++?

std::deque does not support such feature. It is not possible to set a maximum size for it. There isn't any standard container that supports such feature (except technically std::array which has a fixed size).

You can yourself write a custom container that does support such feature. You can use a standard container within the implementation of your custom container if you so prefer. A minimal example, which is by no means complete, nor polished:

struct MaxContainer {
    void push_front(Cart c) {
        if (internal_container.size() < max_size)
            internal_container.push_front(std::move(c));
        else
            ; // do something else
    }
private:
    int max_size;
    std::deque<Cart> internal_container;
}

You could even create a container adaptor, which can adapt any container (with restrictions) and add a max size to it simply by templetizing the internal container type.

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That said, you don't necessarily need to have a container which enforces the size limit. Instead, you could simply refrain from adding more elements into the container in the code that uses it.