![]() This has led to significant fragmentation and limitations in many of these frameworks, especially with more complex application lifecycles. While these solutions have helped to solve the basic problem of reducing glue code, the developer community has never really gravitated towards one (or two) common solutions. Over the years, open-source ORM frameworks emerged, including DBFlow, GreenDAO, OrmLite, SugarORM and Active Android. When Android came on the scene, no ORM existed for the Android environment. The best way to think of it is as a tool designed to automatically generate glue code to map between your object instances and rows in your database. Long before the days of Android, developers in other object-oriented languages started using a class of tool called an ORM to solve this problem. In the early days of Android, if you had a Person object that you wanted to store in the SQLite database, you would have had to create glue code that would turn objects into to SQL and SQL into objects. VALUES ('Grumpy Cat', '1 Tuna Way, Los Angeles CA', '31') INSERT INTO Persons (Name, Address, TelephoneNumber) In order to store and retrieve this data, SQL commands need to be be issued to the database, telling it to retrieve and store the data.įor example, to store a record in a table you might use a command like: Each instance of that person would be a row in that table. With a SQL relational database, you would model the Person class as a table. In our example you could create a class called Person, with the following attributes:įor each person you’d then create an instance of a Person, with unique data for that individual. ![]() ![]() When you are developing applications using an object-oriented programming language like Kotlin, you use classes to represent the data that you are storing. To understand Room, it is helpful to understand the sum of its parts, so let’s start with a simple example of storing the names, addresses and phone numbers of a few people. ![]() Introduction to Android Data Persistence Classes, Tables, Rows and Instances Use the key combination Option-Return on Mac Alt-Enter on PC to resolve any missing dependencies as you work through your project.
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