Awaiting within valueTransformer

[poweriton]

Im not sure if this is a bug or my lack of understanding:

I want to use the valueTransformer method on a signature pad asynchronously while i wait for the signature to upload, however the call doesn't seem to be waiting for the return url before returning the value on submit

 return FormBuilderSignaturePad(
          name: 'signature',
          controller: _controller,
          decoration: InputDecoration(labelText: "signature"),
          initialValue: _signatureFile?.readAsBytesSync(),
          onSaved: (newValue) async {},
          valueTransformer: (value) async {
            final savedUrl = await processSignature(value, context);
            return savedUrl;
          },
          onChanged: (value) {},
        );

the return type when calling SaveAndValidate or Save then Validate is a string representation of the future

if (_currentStep <= _totalSteps - 1) {
                    _formKey[_currentStep].currentState.save();

                    if (_formKey[_currentStep].currentState.validate()) {
                      var request = firestoreDatabase.currentRequest;
                      //Value is in this case "Future<String>" and not "http://urltoimage.co.uk"
                      var value = _formKey[_currentStep].currentState.value;

                      firestoreDatabase.updateRequest(request).then((value) {
                        if (_currentStep == _totalSteps - 1) {
                          //pop the screen
                          Navigator.pop(context);
                        } else {
                          setState(() {
                            _currentStep++;
                          });
                        }
                      });
                    }
                  }

any ideas if this is incorrectly programmed or a bug?

[danvick]

It would be great to have valueTransformer as async. The problem, as it is, is that valueTransformer is called within Flutter's FormField.onSave which itself is synchronous and doesn't await

[awhitford]

@poweriton If you need valueTransformer to be async, then you need to find an alternative strategy to run your async logic... I recommend doing the async logic as part of the Form Submit logic, which could be async.

[ebelevics]

Yeah, this would have been great if valueTranformer would return FutureOr

[deandreamatias]

This still a issue?

[tonypottera24]

@deandreamatias This is still an issue. valueTransformer does not await. This feature is necessary. For example, if I want to upload a MultipartFile. I've to do something as the followings.

valueTransformer: (images) async {
  if (images != null) {
    var multipartFile = [];
    for (final image in images) {
      multipartFile.add(await MultipartFile.fromFile(image.path));
    }
    return multipartFile;
  }
},

[deandreamatias]

@poweriton If you need valueTransformer to be async, then you need to find an alternative strategy to run your async logic... I recommend doing the async logic as part of the Form Submit logic, which could be async.

@tonypottera24 this comment is useful to provide a solution to this. Why you need a MultipartFile in your form? A nice approve with SOLID principles, is you get a image type and transform in your state or data module