problem with char array in a exercise on pointers.

[lilysfather]

Hi, im new to c++ programming and need help to understand why this code isnt working.
I was trying to code an exercise on pointers and structures but couldnt get it to work.
i get this error message:
error C2440: '=' : cannot convert from 'const char [5]' to 'char [20]
I solved it by using string instead of char Array in the structure but im intrested in knowing why it isnt working with an char Array so i might learn something new.

struct candybar
{
	char brand[20];
	double weight;
	int cal;
};

int main()
{
	candybar *p_candy = new candybar[3];

	p_candy[0].brand = "japp";
	p_candy[0].weight = 3.5;
	p_candy[0].cal = 500;

[Cubbi]

C-style arrays are not assignable, so the expression p_candy[0].brand = "japp";, which attempts to assign an array of 5 const char (four letters and a null char) to the array of 20 char cannot be compiled.

strings are assignable, which is why it worked for you with strings.

[TheIdeasMan]

Hi lilysfather

You cannot assign char arrays like that.

In C, you must copy each char individually, or use a library function to do it.

As you have figured out, it is a lot easier in C++ to use strings ...... :-)

HTH

[lilysfather]

Ok, thanks for the fast answers.
It works if i initialize it to "japp" or use cin >> to get user input.
But i cant assaign it like that.guess i have to read the Array chapter again to understand why.
Edit: Figured it out myself.
Should have used something like strcpy(p_candy[0].brand , "japp");
right?

[TheIdeasMan]

lilysfather wrote:

But i cant assaign it like that.guess i have to read the Array chapter again to understand why.
Edit: Figured it out myself.
Should have used something like strcpy(p_candy[0].brand , "japp");
right?

In C++, the std::string class has an overloaded assignment operator, which essentially has code that copies chars individually from one object to the other.

C has no such concept of operator overloading, so one must use a library function which does the copy of the individual chars.

But really you should think about whether you want to do C code or C++, it is seen as bad style to mix C & C++ code - for example using printf instead of cout, or processing things individually when there is an algorithm that does it for you.

As said earlier std::string has lots of very handy things, as does all of the STL.

HTH