Because yield-statement isn't allowed within a callback, how can i use the put feature of redux-saga within a callback?

I'd like to have the following callback:

function onDownloadFileProgress(progress) {

  yield put({type: ACTIONS.S_PROGRESS, progress})

}

This isn't working and ends up in unexpected token, because yield is not allowed in a plain function. Otherwise i can't pass a callback as a function *, that would allow yield. ES6 seems broken here.

I've read that redux-saga provides some features called channels, but to be honest, i didn't get it. I've read several times about these channels and example code, but in all examples they've solved very difficult and different problems, not my simple case and at the end of the day i've got up there.

Can someone tell me a solution how to deal with this issue?

The whole context:

function onDownloadFileProgress(progress) {

  yield put({type: ACTIONS.S_PROGRESS, progress})

}



export function * loadFile(id) {

  let url = `media/files/${id}`;



  const tempFilename = RNFS.CachesDirectoryPath + '/' + id;



  const download = RNFS.downloadFile( {

    fromUrl: url,          

    toFile: tempFilename,  

    background: false,

    progressDivider: 10,

    progress: onDownloadFileProgress,

  })



  yield download.promise;



}