Dio Cache Interceptor Example #

This repository demonstrates how to use a custom cache interceptor with the Dio package to cache HTTP responses in memory. It includes an example of how to configure a Dio instance to cache responses for a specified duration and bypass the cache when necessary.

Features #

• Custom Cache Storage: An in-memory storage for caching the responses.
• Cache Expiration: Cached responses are only returned if they haven't expired, as specified by the duration.
• Cache Bypass: Allows for bypassing the cache with a zero-duration setting.
• Easy Integration with Dio: Simple setup for caching HTTP requests using Dio interceptors.

Components #

1. example/dio_cache_interceptor_example.dart #

This is the main entry point that demonstrates how to use the cache interceptor with Dio.

• It makes multiple HTTP requests to the same URL.
• The first request fetches data from the network and caches it.
• The second request returns the cached response.
• The third request forces a bypass of the cache.
• The fourth request demonstrates fetching the data again from the cache after bypassing.

2. lib/src/cache_interceptor.dart #

This file contains the implementation of the CacheInterceptor, which intercepts the HTTP requests and manages caching logic.

• _getCachedResponse: Retrieves the cached response if it's available and not expired.
• _saveResponseToCache: Saves the HTTP response to the cache storage.
• onRequest: Checks if a cached response is available before making a network request.
• onResponse: Saves the response to the cache after a successful request.
• onError: Handles errors in the request lifecycle.

3. InMemoryCacheStorage Class #

A simple custom cache storage implementation that keeps cached responses in memory (using a Map<String, String>). This class implements the CacheStorage interface, allowing for storing, retrieving, and removing cached responses.

Installation #

1. Add Dio and Dio Cache Interceptor to your pubspec.yaml:

   dependencies:
     dio: ^5.0.0
     simple_dio_cache_interceptor: ^0.4.0
   

2. Install dependencies:

   Run the following command to install the dependencies:

   flutter pub get
   

Usage #

1. Import necessary packages:

   import 'package:dio/dio.dart';
   import 'package:simple_dio_cache_interceptor/simple_dio_cache_interceptor.dart';
   

2. Create the Dio instance with the cache interceptor:

   final dio = Dio();
   final storage = InMemoryCacheStorage();
   final cacheInterceptor = CacheInterceptor(storage);
   dio.interceptors.add(cacheInterceptor);
   

3. Make HTTP requests:

   You can now make HTTP requests with caching enabled. The X-Cache-Duration header determines how long the cache is valid for.

   final response = await dio.get(
     'https://jsonplaceholder.typicode.com/todos/1',
     options: Options(
       headers: {'X-Cache-Duration': Duration(minutes: 10)},
     ),
   );
   

4. Simulate Cache Bypass:

   To bypass the cache for a request, set the X-Cache-Duration header to Duration.zero.

   final response = await dio.get(
     'https://jsonplaceholder.typicode.com/todos/1',
     options: Options(
       headers: {'X-Cache-Duration': Duration.zero},
     ),
   );
   

Example Output #

--- First network call ---
Data: {userId: 1, id: 1, title: "delectus aut autem", completed: false}
Duration: 100ms

--- Second call (from cache) ---
Data: {userId: 1, id: 1, title: "delectus aut autem", completed: false}
Duration: 10ms

--- Third call (cache bypassed) ---
Data: {userId: 1, id: 1, title: "delectus aut autem", completed: false}
Duration: 110ms

--- Fourth call (new cache) ---
Data: {userId: 1, id: 1, title: "delectus aut autem", completed: false}
Duration: 100ms

How it works #

• Cache Duration: When the X-Cache-Duration header is set in a request, the cache will only return the response if it hasn't expired based on the given duration.
• Cache Bypass: Setting the X-Cache-Duration to Duration.zero forces the request to bypass the cache and always fetch the data from the network.
• In-Memory Cache: The cache is stored in memory and will be lost when the app is closed. You can replace InMemoryCacheStorage with another storage solution, such as SQLite or SharedPreferences, for persistent caching.

Note #

This example demonstrates a basic cache usage. If you need more advanced control over your request caching, such as controlling cache strategies, automatic cache expiration, or additional features, check out dio_caches_interceptor.

License #

This project is licensed under the MIT License - see the LICENSE file for details.