How do I implement dio http cache alongside my interceptor - flutter

Question

Here is my interceptor setup :
class AppInterceptor extends Interceptor {
Dio dio = Dio();
Dio previous;
AppInterceptor() {}
AppInterceptor.firebaseIDToken() {
this.dio.interceptors.add(
InterceptorsWrapper(onRequest: (options, handler) async {
var token = await getAuthorizationToken();
options.headers["Authorization"] = 'Bearer $token';
dio.unlock();
handler.next(options);
}, onResponse: (response, handler) {
return handler.next(response);
}, onError: (DioError e, handler) {
return handler.next(e);
}
),
);
}
...
}
And here is how I make http request:
Response response;
if (user != null) {
response = await AppInterceptor.tokenAuthorization()
.dio.get(Global.apiurl + 'jobs/detail/$pageid?
coordinates=$coordinates');
} else {
response = await AppInterceptor.apikey().dio.get(Global.apiurl +
'jobs/detail/$pageid?coordinates=$coordinates');
}
return Job.fromJson(response.data);
Now what I want to do is add the dio HTTP cache interceptor
https://pub.dev/packages/dio_http_cache
dio.interceptors.add(DioCacheManager(CacheConfig(baseUrl: "http://www.google.com")).interceptor);
google.com here should be my Global.apiurl
My question is, how do I go about adding this to my above implementation?

Answer 1

I stumbled upon this problem earlier and actually found my way through Dio's doc. I learned that handler actually have method other than next which is resolve.
To resolve onError with custom Response (in this case, something from your cache), you should resolve the handler instead of passing it through next.
I made the interceptor as it's own class and specifically return cached response only on Connection Timeout & Other Error.
class CacheInterceptor extends Interceptor {
final _cache = <Uri, Response>{};
#override
onRequest(options, handler) => handler.next(options);
#override
onResponse(response, handler) {
// Cache the response with uri as key
_cache[response.requestOptions.uri] = response;
handler.resolve(response);
}
#override
onError(DioError err, handler) {
var isTimeout = err.type == DioErrorType.connectTimeout;
var isOtherError = err.type == DioErrorType.other;
if (isTimeout || isOtherError) {
// Read cached response if available by uri as key
var cachedResponse = _cache[err.requestOptions.uri];
if (cachedResponse != null) {
// Resolve with cached response
return handler.resolve(cachedResponse);
}
}
return handler.next(err);
}
}
And then, add the CacheInterceptor above to the Dio instance
...
dio.interceptors
..add(CacheInterceptor())
..add(LogInterceptor());
...