Red screen after start

[Sebastian Trebunak]

Hello There!

First of all I would like to thank you so much for your article. Next week I'm going to try to implement my first C++ lib to do some heavy-lifting there, instead of JS thread.

Maybe I have not read the article carefully enough yet but I wanted to try it today and see if it is working as it is so I cloned the repo and installed node_modules. Afterwards I've run cd ios && pod install to install cocoapods deps.

and after that I've tried to start the app but without success. I got red screen:

I would like to ask you if there is anything that I've missed in article?

Thank you so so much once again!

[Kudo Chien]

My CxxModule sample code is only for Android because IMO interop between C++ and Obj-C is much easier than JNI.
If you are looking for iOS C++ native module, maybe you could check TurboModule. There are some good sample code already.
https://github.com/facebook/react-native/tree/master/ReactCommon/turbomodule/samples/platform/ios/

[Sebastian Trebunak]

Oh :) thank you so much!

[Kudo Chien]

Well, just found that is not so difficult to add iOS support, so I added it last night.
1d9c0a4
However, still recommend TurbeModule IMO.

[Sebastian Trebunak]

Hello @Kudo I'm finally getting to phase of my project when I need to make a decision about how to implement some heavy calculations. I would like to thank you very much for any answer.

I need to implement some x/y position/gps processing that includes:

• load input data (height map, image screen size, etc.) based on location where the user is currently located at.
• re-calculate X/Y position of sub-images (interactable objects placed at image) based on users real GPS location (these images can be moved manually too so there is a chance that some re-computations may happen too often lets say once per 50ms (depends on throttle's timer value).
• to achieve position recomputation I will need to perform GPS(lat/lon) to UTM conversion.
• read specific bits from binary file (height map) to recalculate height difference between two sub-images.

I would like to ask you if there is even small chance i could use CxxModule for that without loosing too much of ms's during bridge communication.

Code below shows How I think it should work:

• I'm able tomj initialize custom NativeModule with some default data (which are based on current user's location using c++ module). To be more specific I would like to be able to do something like:

...
const {CxxRecomputingModule} = NativeModules;

class RecomputingComponnet extends Component {
    ...
 
    componentDidUpdate() {
        /**
        * get init values for current location (.hgh binary 
        * file's content, image size, ...). Even better would 
        * be if i could send just a path to binary file and read it 
        * directly from C++ but it is an implementation detail 
        * which I will look at and maybe solve later.
        */
        const initValues = this.props.initValues; 
        ...
        CxxRecomputingModule.setInitValues(initValues)
    }

• Then I would like to use these initial values with every other call in order to skip too much of data sending through bridge with every new calculation, so lets say:

...
const {CxxRecomputingModule} = NativeModules;

class RecomputingComponnet extends Component {
   ...

    onPositionChanged = (newX, newY) => {
        /**
        * on the native side, recomputeNewValues() will use these 
        * two params and all values from `setInitValues()` method
        * from previous example.
        */
        CxxRecomputingModule.recomputeNewValues(newX, newY)
            .then((x, y) => {
                this.setState({newX: x, newY: y});
            });
    }

So I think I would implement something like C++ class which will hold default data in member variables and will re-use them with every other call of it's member's method.

Is something like this even possible using CxxModule? I'll be good even with one-word answer like: "Yes" or "No" 😸

Thank you so much once again!