c++ vector to comma delimitated string?

Question

Possible Duplicate:
C++ Vector to CSV by adding Comma after each element

I have a vector:

std::vector<std::pair<int, QString> > recordingArray;

I need to convert it to a comma delimitated string so I can store it in a database (is there a better format for the data - it all needs to go in one field)

How can I convert it to a comma delimitated string?

And then later, convert it back?

I would take a look at boost::algorithm::join and boost::algorithm::split — frankc, Dec 10 '12 at 21:18
Your vector is slightly the same.. the concept is the same either way. It's a duplicate. — , Dec 10 '12 at 21:18
You *could* use the standard library algorithms but I'd prefer to bash it out in a loop. Comma delimiting is as good as any -- provided you remember to escape literal commas, of course. — Elliott, Dec 10 '12 at 21:20
Yeah, why would anyone think about reusing code that works and has been tested when they can reinvent all the bugs on their own. — R. Martinho Fernandes, Dec 10 '12 at 21:46
@R.MartinhoFernandes I would suggest that if you can introduce bugs into a simple concatenation loop then programming might not be for you. — Elliott, Jan 17 '17 at 03:00
Link to answer using boost: https://stackoverflow.com/questions/1833447/a-good-example-for-boostalgorithmjoin — frabcus, May 29 '18 at 09:34

score 17 · Answer 1 · answered Dec 10 '12 at 21:42

17

Use std::transform and a std::stringstream for this.

std::stringstream str;

std::transform(
    recordingArray.begin(),
    recordingArray.end(),
    std::ostream_iterator<std::string>(str, ", "),
    [](const std::pair<int, QString> &p) { return std::to_string(p.first) + ", " + p.second.toStdString(); });

answered Dec 10 '12 at 21:42

moswald

11,491
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aggregate 'std::stringstream str' has incomplete type and cannot be defined – panthro Dec 10 '12 at 21:57
6

Did you really downvote me because you don't know how to google std::stringstream and find out which header to include? – moswald Dec 10 '12 at 22:22
@moswald have an upvote! – Nicu Stiurca Dec 10 '12 at 23:09

score 2 · Answer 2 · answered Dec 10 '12 at 21:19

2

string line = "";
auto it = recordingArray.begin();

while(it != recordingArray.end())
{
  line.append(*it);
  line.append(',');
}

This assumes that each item is directly convertible to a string. You may need to write a toString function.

string toString(std::pair<int, QString>> input)
{
  /* convert the data to a string format */
}

Then call line.append(toString(*it)).

answered Dec 10 '12 at 21:19

lcs

4,227
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3

That will leave a stray `','` on the end. – Lily Ballard Dec 10 '12 at 21:25
Great, thanks very much but it does not name a type? What is 'it'? – panthro Dec 10 '12 at 21:27
Also, how do I get each part of the vector pair, the int and string? – panthro Dec 10 '12 at 21:33
He's using C++03, you should put in the actual type instead of `auto`. – Dan Dec 10 '12 at 21:55
`auto it` expands to `pair::iterator it`. Parts are accessible via `it->first` and `it->second` – lcs Dec 10 '12 at 22:18
1

@user1013512: you need to learn C++ before you try to use std::pair. – Dec 11 '12 at 01:08
I know this post is old, but if you're here like me and you want to leave out the comma at the end then do this: `if(it != --recordingArray.end())` – cael ras Feb 27 '22 at 06:53

c++ vector to comma delimitated string?

2 Answers2

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