Cordova - write to and read from File - ios

Question

I am running into a problem with my cordova app where after an app update, localStorage is cleared. I am now attempting to save some basic user data to a text file instead, using cordova's FileWriter and FileReader.
At some point cordova updated and these methods and now requires a plugin to read and write files: https://cordova.apache.org/docs/en/latest/reference/cordova-plugin-file/index.html
Because my live iOS application uses the old version of cordova, it must write with FileWriter. My app update (not live) uses a newer version of cordova and therefore must use the plugin.
------ Possible workaround found, see update below ------
When trying to read the file, I am seeing the following error in xcode:
017-01-26 17:58:52.990 MyApp[40355:2892997] ERROR: Method 'hello there' not defined in Plugin 'File'
2017-01-26 17:58:52.991 MyApp[40355:2892997] -[CDVCommandQueue executePending] [Line 142] FAILED pluginJSON = ["File1875336264","File","hello there",["cdvfile://localhost/persistent/player_data.txt",null,null]]
Note: I'm running the following code in Safari console while the iOS simulator is running, just for convenience
My code for writing the file
(function() {
var onFail = function(err) {
alert('write action failed!');
alert(err.code);
};
var onGotFS = function(fileSystem) {
alert( 'gotFS' );
fileSystem.root.getFile("player_data.txt", {create: true}, onGotFileEntry, onFail);
};
var onGotFileEntry = function(fileEntry) {
alert( 'gotFileEntry, path: ' + fileEntry.fullPath );
fileEntry.createWriter(onGotFileWriter, onFail);
};
var onGotFileWriter = function(writer) {
alert( 'gotFileWriter' );
writer.onwrite = onFileWritten;
writer.onerror = onFail;
var data = "hello there";
alert( 'writing data: ' + data );
writer.write( data );
};
var onFileWritten = function(evt) {
alert( "saveTokenToFile SUCCESS!" );
};
// start process of looking up file system and writing
alert( 'requesting file system ...' );
window.requestFileSystem(LocalFileSystem.PERSISTENT, 1024, onGotFS, onFail);
})();
My code for reading the file:
(function() {
window.requestFileSystem(LocalFileSystem.PERSISTENT, 0, function (fs) {
fs.root.getFile("player_data.txt", { create: true }, function (fileEntry) {
fileEntry.file(function (file) {
var reader = new FileReader();
reader.onloadend = function() {
alert("Success");
console.log(evt.target.result);
};
reader.onerror = function() {
console.log("reader error");
};
reader.readAsText(file);
}, onErrorReadFile);
});
}, onErrorLoadFs);
var onErrorReadFile = function(){
console.log("error reading file");
}
var onErrorLoadFs = function() {
console.log("request file system has failed to load.");
}
})();
UPDATE
In case anyone else runs into this, I did find a way to read the saved file. The fileEntry object has a URL path to the saved file. To access the data on the file, I'm passing that URL to jQuery.getJSON, which gives us back some readable json.
readDataFromFile: function(){
window.requestFileSystem(LocalFileSystem.PERSISTENT, 0, function (fs) {
fs.root.getFile("player_data.txt", {}, function (fileEntry) {
var entryURL = fileEntry.nativeURL;
jQuery.getJSON(entryURL, function(data) {
console.log(data);
}).fail(function(){
console.log("file found, but contents were empty");
});
}, onErrorGetFile);
}, onErrorLoadFs);
var onErrorLoadFs = function() {
console.log("request file system has failed to load.");
};
var onErrorGetFile = function() {
console.log("requested file can not be read or does not exist");
};
}