Using string functions (.substr) on arrays of strings

Question

I have an array of strings, and need to grab substrings (the strings in between commas, in this case) and put them into another array of strings.

I declare it as strings[numberOfTapes], so when I am searching for the commas I go character by character in a nested for loop, like so:

for(int j = 0; j < tapes[i].length(); j++){
   if(tapes[i][j] == ','){
      input[counter2] = tapes[i][j].substr(i-counter, counter);
   }
}

For which I get the following error:

request for member 'substr' in tapes[i].std::basic_string::operator[]
[with _CharT = char, _Traits = std::char_traits, _Alloc = std::allocated]
(((long unsigned int)))', which is of non class type 'char'

I'm going through the string character by character with j. Is there a way to get .substr to work with the tapes[i][j] format, or do I need to implement this differently to work?

sth · Accepted Answer · 2010-02-04 04:00:24Z

1

tapes[i][j] is the character ',', and that character has no substr method. You probably wanted to call substr on the string object tapes[i], not on the single character.

Also: You call substr(i-counter, counter) after you found a comma at position j. Is that your intention?

answered Feb 4, 2010 at 4:00

sth

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Seadog · Accepted Answer · 2010-02-04 04:00:26Z

1

If it's an array of strings, tapes[i][j] will access a char, not the string that you wish to substring, you probably want tapes[i].substr...

answered Feb 4, 2010 at 4:00

Seadog

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Rakesh K · Accepted Answer · 2010-02-04 04:05:43Z

0

If comma(,) is used as a delimiter in your case, why not using some function which splits the strings based on a delimiter?

I can think of using something like strtok() function to split them based on comma(,).

Rakesh.

answered Feb 4, 2010 at 4:05

Rakesh K

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Roger Pate · Accepted Answer · 2010-02-04 04:14:45Z

0

Using higher-level tools rather than individually iterating each string in a sequence of strings:

#include <iostream>
#include <sstream>
#include <string>
#include <vector>

int main() {
  using namespace std;
  istringstream input ("sample,data,separated,by,commas");
  vector<string> data;
  for (string line; getline(input, line, ',');) {
    data.push_back(line);
  }

  cout << "size: " << data.size() << '\n';
  for (size_t n = 0; n != data.size(); ++n) {
    cout << data[n] << '\n';
  }
  return 0;
}

Also look at std::string's various methods (it has a lot, described as "too many plus the kitchen sink"), you can use find to simplify your loop as a first step.

answered Feb 4, 2010 at 4:14

Roger Pate

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