Question

Basically, I’m passing a pointer to a character string into my constructor, which in turn initializes its base constructor when passing the string value in. For some reason strlen() is not working, so it does not go into the right if statement. I have checked to make sure that there is a value in the variable and there is.

Here is my code, I’ve taken out all the irrelevant parts:

Label class contents:

Label(int row, int column, const char *s, int length = 0) : LField(row, column, length, s, false)
{
}

Label (const Label &obj) : LField(obj)\
{
}

~Label()
{
}

Field *clone() const
{
    return new Label(*this);
}

LField class contents:

LField(int rowNumVal, int colNumVal, int widthVal, const char *valVal = "", bool canEditVal = true)
{ 
    if(strlen(valVal) > 0)
    {
    }
    else
    {
        //This is where it jumps to, even though the value in
        //valVal is 'SFields:'
        val = NULL;
    }
}

Field *clone() const
{
    return new LField(*this);
}

LField(const LField &clone) { 
    delete[] val;
    val = new char[strlen(clone.val) + 1]; 
    strcpy(val, clone.val);
    rowNum = clone.rowNum;
    colNum = clone.colNum;
    width = clone.width;
    canEdit = clone.canEdit;
    index = clone.index;
}

Screen class contents:

class Screen {
    Field *fields[50];
    int numOfFields;
    int currentField;
public:
    Screen()
    {
        numOfFields = 0;
        currentField = 0;
        for(int i = 0; i < 50; i++)
        fields[i] = NULL;
    }


    ~Screen()
    { 
        for (int i = 0; i < 50; i++)
            delete[] fields[i]; 
    }

    int add(const Field &obj)
    {
        int returnVal = 0;
        if (currentField < 50)
        {
            delete[] fields[currentField];
            fields[currentField] = obj.clone();   
            numOfFields += 1;   
            currentField += 1;      
            returnVal = numOfFields;    
        }
        return returnVal;
    }

    Screen& operator+=(const Field &obj)
    {
        int temp = 0;
        temp = add(obj);
        return *this;
    }
};

Main:

int main () {
    Screen s1;
    s1 += Label(3, 3, "SFields:");
}

Hopefully someone is able to see if I am doing something wrong.

Answer 1

Marcin at this point the problem will come down to debugging, I copied your code with some minor omissions and got the correct result.

Now it needs to be said, you should be using more C++ idiomatic code. For instance you should be using std::string instead of const char* and std::vector instead of your raw arrays.

Here is an example of what the LField constructor would look like with std::string:

#include <string> // header for string

  LField(int rowNumVal, 
         int colNumVal, 
         int widthVal, 
         const std::string& valVal = "", 
         bool canEditVal = true)
  {
    std::cout << valVal;
      if(valVal.length() > 0)
      {
      }
      else
      {
          //This is where it jumps to, even though the value in
          //valVal is 'SFields:'
          //val = NULL;
      }
  }

Using these types will make your life considerably easier and if you make the change it may just fix your problem too.

PREVIOUS:
So you can be CERTAIN that the string is not being passed in correctly add a printline just before the strlen call. Once you do this work backward with printlines until you find where the string is not being set. This is a basic debugging technique.

Label(int row, 
            int column, 
            const char *s, 
            int length = 0) : 
                LField(row, column, length, s, false) {
  }

    LField(int rowNumVal, 
                     int colNumVal, 
                     int widthVal, 
                     const char *valVal = "", 
                     bool canEditVal = true) 
        { 
            std::cout << valVal << std::endl;
            if(strlen(valVal) > 0) 
            {

            }
            else {
                            //This is where it jumps to, even though the value in
                                                                    //valVal is 'SFields:'
                val = NULL;
            }
        }