How to save a vector of a custom type of elements on disk, read it, and parse it into a vector again using C++ - c++

Question

The vector type is TrackInfo:
class TrackInfo
{
public:
TrackInfo(URL& _url, String& _title, double& _length, String _fileFormat);
URL url;
String title;
double length;
String fileFormat;
};
====================================================================================
std::vector<TrackInfo> tracks;
TrackInfo track(fileURL, fileName, length, fileFormat);
tracks.push_back(track);
tracks.push_back(track);
So, how can I save this vector on the computer and then reread it when I need and convert the file into the same vector again?

Answer 1

I used nlohmann JSON. You can find it here -> https://json.nlohmann.me/
My code:
std::vector<TrackInfo> StoreData::jsonToTrackInfo(json jsonFile)
{
std::vector<TrackInfo> tracks;
for (json jsonf : jsonFile["Playlist"])
{
// Try to parse the data. If there is an error, return the empty vector.
// If one of the Playlist tracks has a problem, it won't be parsed and will parse the rest of the playlist.
try
{
String urlString = jsonf["url"];
String title = jsonf["title"];
double length = jsonf["length"];
String format = jsonf["format"];
URL url { urlString };
TrackInfo track(url, title, length, format);
tracks.push_back(track);
}
catch (const std::exception&)
{
//..
}
}
return tracks;
}
json StoreData::trackInfoToJson(std::vector<TrackInfo> tracks)
{
json j;
// Convert each track into JSON data.
for (TrackInfo track : tracks)
{
j.push_back(
{
{"url" , track.url.toString(false).toStdString()},
{"title" , track.title.toStdString() },
{"length", track.length},
{"format", track.fileFormat.toStdString()}
}
);
}
json jsonFile;
jsonFile["Playlist"] = j;
return jsonFile; // return the Json File
}
and the output of the JSON file should look like this:
{
"Playlist": [
{
"format": ".mp3",
"length": 106.0,
"title": "c_major_theme.mp3",
"url": "file:///C%3A/Users/me/Desktop/tracks/c_major_theme.mp3"
},
{
"format": ".mp3",
"length": 84.0,
"title": "fast_melody_regular_drums.mp3",
"url": "file:///C%3A/Users/me/Desktop/tracks/fast_melody_regular_drums.mp3"
}
]
}
You can find helpful examples here on their website: https://json.nlohmann.me/api/basic_json/#non-member-functions
I hope you find this a helpful answer :D