Assign different values to different struct variables using loop

Question

I have a struct of Examinee like below (each has 1 id and their scores of different subjects):

struct Examinee
{
    string id;
    float math, literature, physic, chemistry, biology, history, geography, civic_education, natural_science,
          social_science, foreign_language;
};

Now i want to write a function that reads from a string different values and assign them to an Examinee. The string looks like this (each info is separated by a comma):

BD1200001,9,4.0,5.0,10,3.5,7.5,4.25,7.0,7.75,9.25,2.0

This is what i have done so far:

Examinee readExaminee(string line_info) {

//turn line_info to char*
    int Line_info_length = line_info.length();
    char* info = new char[Line_info_length + 1];
    strcpy(info, line_info.c_str());

//create examinee
    Examinee examinee;

//read id into examinee by token
    char* token = strtok(info, ",");
    examinee.id = token;

//read score and assign to subjects
    while (token != NULL)
    {
        float score = strtof(token, NULL);

        //assign score to appropriate subject

        token = strtok(NULL, ",");
    }

    delete[] info;
    return examinee;
}

The question is: Can i assign each score to each subject in while loop like above? How can i do that? If not, is assigning each score manually the only way?

Because float fields lay in memory in order, you may assign to *(&math + i) in loop. But I do not suggest to do things like that. I would use map<string, float> scors and obtain string from some build-in array or csv headers string headers[]{"math",...} and assign in loop to score[headers[i]] = val[i] . — Askold Ilvento
– Askold Ilvento, Commented Nov 8, 2020 at 14:12

Igor Tandetnik · Accepted Answer · 2020-11-08 14:05:29Z

2

I'd change the design of Examinee. Something along these lines:

struct Examinee
{
  enum Subject {kSubjMath, kSubjLiterature, ..., kSubjForeignLanguage, kSubjCount};
  string id;
  float scores[kSubjCount];
};

This way you can access scores in a loop, e.g.

for (int subj = 0; subj < Examinee::kSubjCount; ++subj) {
 examinee.scores[subj] = some_score;
}

Or access specific score as examinee.scores[Examinee::kSubjLiterature]

If you are unable or unwilling to change Examinee, you can sort of simulate this locally:

Examinee examinee;
float* scores[] = {&examinee.math, &examinee.literature, ..., &examinee.foreign_language};
for (int subj = 0; subj < std::extent_v<scores>; ++subj) {
  *scores[subj] = some_value;
}

answered Nov 8, 2020 at 14:05

Igor Tandetnik

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