A database is an organized collection of data, which supports the storage and manipulation of data and accessed electronically from a computer system. We can organize data into rows, columns, tables, and indexes. It makes data management easy. We can store many things in the database, like name, age, picture, image, file, pdf, etc. Flutter provides many packages to work with the database. The most used and popular packages are: SQLite Database SQLite is a popular database software library that provides a relational database management system for local/client storage. It is a light-weight and time-tested database engine and contains features like self-contained, server-less, zero-configuration, transactional SQL database engine. Flutter SDK does not support SQLite directly. Instead, it provides a plugin sqflite, which performs all operations on the database as similar to the SQLite library. The sqflite provides most of the core functionalities related to the database are as follows: Let us see step by step how we can store and fetch data in the Flutter. Step 1: First, create a new project in Android Studio and add the dependencies in pubspec.yaml file. Step 2: Create a model class. In this step, we have to define the data that needs to be stored before creating a table to store information. The following code explains it easily. Step 3: Open the database. Here, we need to open the connection to the database. It requires two steps: Step 4: Create the table. In this step, we have to create a table that stores information about the books. Here, we are going to create a table named books, which contains the id, title, and price of the books. They are represented as three columns in the book table. Step 5: Insert a Book into the database. Here, you have to store information on the table about the various books. Inserting a book into the table involves two steps: The following code explains it more clearly. Step 6: Retrieve the list of books. Now, we have stored the book into the database, and you can use a query to retrieve a particular book or list of all books. It involves two steps: You can see the following code to understand it easily. Step 7: Update a Book in the database. You can use an update() method to update the book that you want. It involves two steps: You can see the following code to understand it. Step 8: Delete a Book from the database. You can use the delete() method to delete the database. For this, you need to make a function that takes an id and delete the database of the matching id. Let us see the complete code to understand how we can create a database file with sqflite plugin. For this, create a new Flutter project and the sqflite and path package into the pubspec.yaml file. Next, create a new file into the lib folder and insert the following code in this file. Now, connect the database with your UI and run the code.

In this section, we are going to learn how we can access the REST API in the Flutter app. Today, most of the apps use remote data using APIs. So, this section will be the important part for those developers who want to make their carrier in Flutter. Flutter provides http package to use http resources. The http package uses await and async features and provides many high-level methods such as read, get, post, put, head, and delete methods for sending and receiving data from remote locations. These methods simplify the development of REST-based mobile applications. The detail explanation of the core methods of the http package are as follows: Read: This method is used to read or retrieve the representation of resources. It requests the specified url by using the get method and returns the response as Future<String>. Get: This method requests the specified url from the get method and returns a response as Future<response>. Here, the response is a class, which holds the response information. Post: This method is used to submit the data to the specified resources. It requests the specified url by posting the given data and return a response as Future<response>. Put: This method is utilized for update capabilities. It updates all the current representation of the target resource with the request payloads. This method request the specified url and returns a response as Future<response>. Head: It is similar to the Get method, but without the response body. Delete: This method is used to remove all the specified resources. The http package also provides a standard http client class that supports the persistent connection. This class is useful when a lot of requests to be made on a particular server. It should be closed properly using the close() method. Otherwise, it works as an http class. The following code explains it more clearly. To fetch data from the internet, you need to follow these necessary steps: Step 1: Install the latest http package and add it to the project. To install the http package, open the pubspec.yaml file in your project folder and add http package in the dependency section. You can get the latest http package here and add it like: You can import the http package as: Step 2: Next, make a network request by using the http package. In this step, you need to make a network request by using the http.get() method In the above code, the Future is a class that contains an object. The object represents a potential value or error. Step 3: Now, convert the response getting from network request into a custom Dart object. First, you need to create a Post class. The Post class received data from the network request and includes a factory constructor, which creates Post from JSON. You can create a Post class as below: Now, you have to convert the http.response to a Post. The following code updates the fetchPost() function for returning a Future<Post>. Step 4: Now, fetch the data with Flutter. You can call the fetch method in the initState(). The following code explains how you can fetch the data. Step 5: Finally, display the data. You can display the data by using the FutureBuilder widget. This widget can work easily with async data sources. Let us see the complete code to understand how Flutter works with REST API to fetch data from the network. You can learn more in detail from here. The JSON file is shown below.