How to fail a request?

[scott-mueller]

Hi, I am using typescript with React Native and node. I need to add an interceptor to check for reachability by verifying whether the device has a network connection. How do I cause a request to fail from within the 'request' block. I have tried throwing an error but I get an 'unhanded promise rejection' error instead.

Here is my code:

//register the new interceptor
        ReachabilityFetchInterceptor._unregisterInterceptor = registerFetchIntercept({
            request: async (url: string, options: any): Promise<Array<string>> => {
                //Check whether the url matches the regexp

                //check whether react native thinks we're offline
                NetInfo.getConnectionInfo().then((connectionInfo) => {
                    if (connectionInfo.type === "NONE" || connectionInfo.type === "UNKNOWN") {
                        throw new Error("Reachability Error - Device offline");
                    }
                }).catch((err) => {                    
                    return Promise.reject(err);
                });
           },
           requestError: (error: any): Promise<void> => {
               //do something here after the error is caught 
},
...

i'd love some advice on how to proceed with this?

thanks!

[mlegenhausen]

Your current code does not return the promise. and you are using an async function. Your code should look something like this:

registerFetchIntercept({
  request: async (url: string, options: any): Promise<[string, any]> => {
    //Check whether the url matches the regexp

    //check whether react native thinks we're offline
    const connectionInfo = await NetInfo.getConnectionInfo();
    if (connectionInfo.type === "NONE" || connectionInfo.type === "UNKNOWN") {
      throw new Error("Reachability Error - Device offline");
    }

    return [url, options];
  },
  requestError: (error: any): Promise<void> => {
  }
})

Does this what you want?

[scott-mueller]

No, I need a way to make the code enter the 'requestError; block from within the 'request' block. So far just returning an error, or rejecting the promise doesn't cause that to happen

[mlegenhausen]

Try to register two times. Each registration stands for a then(request, requestError) block. So when you raise an error in request you have a second then like then(request).then(null, requestError). Also try to vary the order of the rigistrations cause internally the registration will be executed in reverse order.

registerFetchIntercept({
  requestError: (error: any): Promise<void> => {
  }
});

registerFetchIntercept({
  request: async (url: string, options: any): Promise<[string, any]> => {
    //Check whether the url matches the regexp

    //check whether react native thinks we're offline
    const connectionInfo = await NetInfo.getConnectionInfo();
    if (connectionInfo.type === "NONE" || connectionInfo.type === "UNKNOWN") {
      throw new Error("Reachability Error - Device offline");
    }

    return [url, options];
  }
});

Maybe this helps.