Why can't I copy a string pointed by a pointer to an array of char

[mendozae]

Hi and help,

I have this function in a class: and a private declaration: how can I copy the parameter "ProductName" to allowedProductName. I tried all combination and I can't get it to compile.

private:
        StatusPanel &statusPanel;
        char allowedProductName[MAX_NAME_LENGTH];
        DeliveryChute &deliveryChute;
        Product *products[MAX_PRODUCTS];
        unsigned productCount;
        unsigned productPriceCents;

// There are only three product name, so if the parameter *productName is either Pepsi, Coke or 7 Up then the
// product is a valid product.
bool
Project1::ProductRack::isCompatibleProduct(const char *productName) const
{
    // Done: Implementing 
    const char FIRST_PRODUCT[] = "Pepsi";
    const char SEC_PRODUCT[] = "Coke";
    const char THIRD_PRODUCT[] = "7 Up";
    if (strcmp(productName, FIRST_PRODUCT ) || strcmp(productName, SEC_PRODUCT) || strcmp(productName, THIRD_PRODUCT))
    {
        //allowedProductName[] = productName; does not work
        //allowedProductName = productName; does not work
        //strcpy (&allowedProductName[0], productName); does not work
        //strcpy(allowedProductName, productName); does not work
        //strcpy(*allowedProductName, productName); does not work
        return true;
    }
    else
        return false;
}

[ne555]

`Does not work' is not and error message

[Cubbi]

How about

bool Project1::ProductRack::isCompatibleProduct(const string& productName)
{
    const char* FIRST_PRODUCT = "Pepsi";
    const char* SEC_PRODUCT = "Coke";
    const char* THIRD_PRODUCT = "7 Up";
    if(productName == FIRST_PRODUCT || productName == SEC_PRODUCT || productName == THIRD_PRODUCT)
    {
        allowedProductName = productName;
        return true;
    }
    else
        return false;
}

(given string allowedProductName;of course)

[Smac89]

@Cubbi, he already tried that method and said it did not work which is kinda surprising to me because that looks like it should work

[mendozae]

Cubbi,

I did not explain my question correctly. I cannot change the type of the
variable allowedProductName. It is a part of the specification by the instructor. and it is a private component of a class. so it stays

char allowedProductName[MAX_NAME_LENGTH];


ne555,

I was the one who put "does not work" to tell the reader that I already tried it and it did not work. All that are commented have been tried and failed to compile.

So I still is looking for a solution.

[K0T4K0t4]

Do you have to have isCompatibleProduct a const function? because making not const would allow you to use strcpy.
or even better since the function returns a bool dont do the assignment in the function and if it returns true you do the assignment else you dont...

in short you cant do this because its a const function and const functions arent supposed to be allowed to edit the object thats calling it. they are read only if you will.

[sam806]

The problem you might be having is that MAX_NAME_LENGTH might not be big enough to contain all the characters(including null character) of productName.
Either you increase MAX_NAME_LENGTH considerably large enough and try

strcpy(allowedProductName, productName);

or else use

strncpy(allowedProductName, productName, sizeof(allowedProductName));

[mendozae]

Kot4Kot4,

You are right the method is a const as shown:
bool
Project1::ProductRack::isCompatibleProduct(const char *productName) const

This means I cannot modify my private variables. And the specification does not allow me to add other method to access the private.

I guess my instructor wants us to think.

[mendozae]

Just in case I missed to mention the method
bool
Project1::ProductRack::isCompatibleProduct(const char *productName) const

and the variable char allowedProductName[MAX_NAME_LENGTH];

are component of a class ProductRack.

[vlad from moscow]

As the member function has const qualifier you can not change array allowedProductName. But you can do it if you will define the array as mutable data member.