React-native-fs: Async/Await issues with readFile() ?

[expaand]

I could not get readFile() to work with async/await correctly. I wanted a function to return results from readFile converted to json, using await to wait for the read to complete. Something like this:

async function func() {
  const path = "abc";
  let contents;
  contents = await RNFS.readFile(path);
  let j = json.parse(contents);
  return j;
}

Then I would simply call this function (in another function):
val = func()

But it appeared that func() returned immediately before the file was actually read. That is not what I was expecting. When using the promise directly and .then syntax, everything was fine.

Not sure if I am totally wrong about how to do this, or if there is an issue. Thanks!

[krzysztof-miemiec]

When you do val = func(), val contains the Promise, not the result of promise. You have to await your func, which returns a promise returning parsed file, i.e. val = await func(). When you use such syntax, the containing function also has to be async.

[expaand]

Thanks, my mistake.

[ToJen]

I'm having a similar issue and it's really confusing.

export const getPaths = async (pathsUpdated) => {
  let filesList = []
  internal = '/sdcard/Download/place'
  external = '/storage/1111-2222/Download/place'

  intPaths = await getFilePaths(internal)
  extPaths = await getFilePaths(external)

  filesList.push(intPaths)
  filesList.push(extPaths)

  console.log("filesList\t" + filesList)  // filesList  [object Object],[object Object]

  return filesList
}

// attempt 1
getFilePaths = async (path) => {
  console.log('reading from:\t' + path)  
  let files = await RNFS.readDir(path)
  console.log("found:\t" + files)   // found:   [object Object]
  return files
}

[krzysztof-miemiec]

If you want to console.log an object, you can do it like this:

  console.log("found:\t" + JSON.stringify(files))   // found:   {"something":{"blah":"x"}}

[ToJen]

This is my second version. What could possibly be wrong?

export const getPaths = async (pathsUpdated) => {
  let filesList = []
  internal = '/sdcard/Download/place'
  external = '/storage/1111-2222/Download/place'

  intPaths = await getFilePaths(internal)
  extPaths = await getFilePaths(external)

  filesList.push(intPaths)
  filesList.push(extPaths)

  console.log(filesList)

  return filesList
}

getFilePaths = async (path) => {
  console.log('reading from:\t' + path)
  let files = await RNFS.readDir(path)
  console.log("found:\t" + JSON.stringify(files))
  return files
}

[ToJen]

Error: Attempt to get length of null array but I'm sure there are files in there. It was working just yesterday.

[krzysztof-miemiec]

Ah, according to this thread on StackOverflow Android will return null when path does not exist. Can you first try to check if the directory exists?

[ToJen]

Yeah it does

[krzysztof-miemiec]

There is one more option, you may miss the following permission in your AndroidManifest.xml:

 <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />

[ToJen]

I updated that and did a ./gradlew clean && ./gradlew installDebug. I don't know what's wrong here.

[krzysztof-miemiec]

Me neither 😞

[tahir-jamil]

any updates?