Uploading an image with redux-form

Question

I have a react.js redux-form that works and posts data back to my API but I need to also allow the submitter to upload an image with the form, ideally with a preview. I struggled a bit and have arrived at dropzone.js but I can't seem to get my form to actually POST the image data back.

render () {
  const FILE_FIELD_NAME = 'files';

    const renderDropzoneInput = (field) => {
      const files = field.input.value;
      return (
        <div>
          <Dropzone
            name={field.name}
            onDrop={( filesToUpload, e ) => field.input.onChange(filesToUpload)}
          >
            <div>Try dropping some files here, or click to select files to upload.</div>
          </Dropzone>
          {field.meta.touched &&
            field.meta.error &&
            <span className="error">{field.meta.error}</span>}
          {files && Array.isArray(files) && (
            <ul>
              { files.map((file, i) => <li key={i}>{file.name}<img src={file.preview}/></li>) }
            </ul>
          )}
        </div>
      );
    }

    return (
        <form onSubmit={this.props.handleSubmit(this.onSubmit)}>
          <div className="form-group">
            <Field name="files" component={renderDropzoneInput} />
          </div>
          <button type="submit" className="btn btn-default">Submit</button>
        </form>
    );
}

The files variable does get POSTed back to the API which is great but it contains the following:

[preview=blob:http://localhost:3000/bed3762e-a4de-4d19-8039-97cebaaca5c1]

Can anyone suggest how I get the actual binary data in to that variable please?

The full code is available here https://github.com/rushughes/dsloracle/blob/master/client/src/components/LandCreate/index.js

Answer 1

I recently had a similar issue and solved it by using the FileReader API to convert the blob url to Base64 (can also convert to binary string).

Then you send the Base64 or binary string to the server.

My example code:

onDrop(acceptedFiles: any): any {

    let images: any = this.state.Images;

    acceptedFiles.forEach((file: any) => {

        const reader: FileReader = new FileReader();
        reader.onload = () => {
            const fileAsBase64: any = reader.result.substr(reader.result.indexOf(",") + 1);
            images.push(fileAsBase64);
        };

        reader.onabort = () => console.log("file reading was aborted");
        reader.onerror = () => console.log("file reading has failed");

        reader.readAsDataURL(file);
    });

    this.setState(prevState => ({   
         Images: images,
    }));
}

If you want to send a binary string instead of base64 change reader.readAsDataURL(file); to reader.readAsBinaryString(file);

and this line: const fileAsBase64: any = reader.result.substr(reader.result.indexOf(",") + 1); can be simplified to const file: any = reader.result;

Answer 2

Here are the steps for file-upload feature: (How to handle image data in your API)

• Append your redux-form values to the FormData instance.

  let formData = new FormData();
  formData.append('myFile', files[0]);
  

• Send multipart/form-data request from Client to your API with axios or fetch library:

• Receive that multipart/form-data request in your API, process it with multer and then write the file to the disk storage or memory storage as follows:

  $ npm install --save multer
  

  const multer  = require('multer')
  
  const storage = multer.diskStorage({
    destination: function (req, file, cb) {
    cb(null, '/tmp/my-uploads')
   },
    filename: function (req, file, cb) {
    cb(null, file.fieldname + '-' + Date.now())
   }
  })
  
  const upload = multer({ storage: storage })
  
  const app = express()
  
  app.post('/upload', upload.single('myFile'), (req, res, next) => {
    // req.file is the `myFile` file
    // req.body will hold the text fields, if there were any
   })
  

• (Optional) Serve files directly from your API with Express Serve-Static