strcpy

This is a discussion on strcpy within the C++ Programming forums, part of the General Programming Boards category; I'm trying to assign a string to a string array, but I keep getting the 'cannot convert parameter' error. Here's ...

  1. #1
    843
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    strcpy

    I'm trying to assign a string to a string array, but I keep getting the 'cannot convert parameter' error. Here's the syntax I'm using:

    Code:
    string data;
    string *cargo_name_array;
    cargo_name_array = new string[n+1];
    strcpy(cargo_name_array[i], data);

  2. #2
    and the hat of wrongness Salem's Avatar
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    strcpy copies C-style char arrays, not C++ style std::string objects.

    The regular assignment operator is used to assign one string to another.
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
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  3. #3
    843
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    How else can I assign a string to an array?

  4. #4
    a_capitalist_story
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    Simple assignment to the array element:
    Code:
    cargo_name_array[i] = data;

  5. #5
    843
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    So that wasn't the problem. I'm confused because the test lines at the bottom still do not work. The strings are not stored correctly:

    Code:
            ifstream cargo_in("cargo_input.txt"); //opens input file
    
            //gets number of lines
            if (cargo_in.is_open()) {
                while (cargo_in.good()) {
                    getline(cargo_in,data);
                    n++; //line counter up
                };
            }
    
            else { //file access verification
                cout << "Input file access error.";
                return 0;
            };
    
            cargo_in.clear();
    
            //declares dynamic arrays for cargo parameters
            cargo_name_array = new string[n+1];
            cargo_duration_array = new int[n];
            cargo_size_array = new int[n];
    
            for (i=1; i<n+1; i++) {
                getline(cargo_in, data, '\t'); //gets string until tab
                cargo_name_array[i] = data; //stores string in array
    
                while (cargo_in.get() == '\t'); //discards consecutive tabs
                cargo_in.unget(); //moves back one character
    
                getline(cargo_in, data, '\t'); //gets size string until tab
                //converts string to decimal and stores size value
                cargo_size_array[i] = (int) strtod(data.c_str(), NULL);
    
                getline(cargo_in, data); //gets duration string
                //converts string to decimal and stores duration value
                cargo_duration_array[i] = (int) strtod(data.c_str(), NULL);
            }
                cargo_in.close(); //closes input file
        }
    
        cargo cargo1;
        cargo *ptr;
        ptr = &cargo1;
    
        ptr->name = cargo_name_array[1];
        ptr->size = cargo_size_array[1];
        ptr->duration = cargo_duration_array[1];

  6. #6
    a_capitalist_story
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    Arrays are always indexed starting at 0 and ending at size - 1. Do not attempt to do otherwise...that way lies madness! Also, using parallel arrays as you are is an ugly solution. You should consider using a class, or at least a struct.

    Why not print out the value of cargo_name_array[i] right after you set it, to ensure it's what you think it should be? Barring that, learning how to use the debugger would be useful.

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