One of the most important components of modern applications is data storage. In an ever connected world, data is involved in almost everything. One of the things a developer has to consider when creating an application is how to store this data in a way that leads to the best experience for the user. In this article, we are going to look at databases for iOS including hosting options and database types, and look to answer the question, “Which is the best iOS database?”
A database for iOS is a database intended specifically for use in persisting data in iOS applications. It often stores data locally on the device to enable access to the data even when offline, due to the ever changing network connectivity of an iOS device.
The most common database on iOS is SQLite, as this is included in the iOS SDKd, thus available to developers out of the box. We will discuss SQLite and other database options later in the article.
Although databases all provide the ability to store, query, and manipulate data, not all databases are created equal.
Before deciding on the best database for your iOS application, you need to know the requirements of your application. Here are two questions that can help you identify these:
1. What sort of data will you be storing?
Are you going to store structured or unstructured data or even large files? Should the data be available across multiple users and/or devices, or can it be stored only on the device?
2. How will the data be accessed?
Will the data be stored across multiple data sources, requiring complex queries to join the data?
There are multiple different database providers that are compatible with iOS but they broadly fall under three categories: relational database, key-value database, and object-oriented database.
Relational database - Data is stored in tables. The tabular format uses keys to form relationships between the tables. The most common example for iOS databases is SQLite using Core Data as a persistence framework. This is the choice if the relationship between the data is heavily connected.
Where a database is located, aka hosted, is an important factor with iOS databases. The following factors, therefore, are worth considering:
Local storage - Having the data available offline by storing it locally is an important feature in mobile applications. Internet connection can be inconsistent on mobile devices. With data stored locally, apps continue to be functional, even when offline, leading to a much better user experience.
Cloud storage - Data sharing across devices and a centralized back end is a common feature of iOS applications. However, this functionality is not supported by local-only storage solutions. To overcome this, mobile developers will need to save the data from their apps to the cloud or a self-hosted server. A cloud database has several advantages over traditional storage.
For example, MongoDB Atlas, MongoDB’s multi-cloud application data platform, MongoDB’s multi-cloud application data platform, combines a flexible document model and unified query interface with automated horizontal and vertical scaling, fexibility, easier database sharing between project types (including mobile), and much more, to provide a first-class developer experience. However, the driver used to communicate with Atlas requires network access at all times, meaning a less optimal user experience when offline or with a slow connection.
There are a few advantages to consider that make object-oriented the best database type for iOS apps:
1. Simplicity
Swift, like Objective-C, is an object-oriented programming language, which means that the data being persisted to a database will start out as objects in the application code. If the data was being persisted into a relational database, an object relational mapper (ORM) would need to be used to convert these objects into the tabular, row-based storage of relational databases. This ORM takes additional time and code to implement, slowing down development time.
Object-oriented databases were created to keep the data consistent between how it’s used in code and where it’s stored. This means it’s a great solution for iOS apps written with Swift, because there won’t be a need to map the objects for data persistence. Complex data can be stored as objects, avoiding any potential unintended consequences due to the conversion to a row in a relational database table.
2. Performance
Sometimes, there will be complex object-to-object relationships between the data. By using an object-oriented database, queries across those objects will be much faster.
3. Readability
The data is much easier to read, both in the database and when used in the application, because it shares the same shape.
There are, in fact, many use cases for using an object-oriented database for iOS. Due to its general purpose object-oriented language, Swift is a natural fit for object-oriented databases and can be used whenever there are objects in code that need to be persisted.
This is the most well known relational database across both iOS and Android.
Core Data is actually an object graph management framework rather than a database itself. It’s therefore paired with a database, most often SQLite. It can, however, also be used to store data in XML, in-memory, and binary formats.
Firebase is a mix of features that can be mixed and matched to fit app requirements. One of these is a realtime database. It’s a cloud-based key-value store with sync capabilities.
This is an interface for access to a key-value database for storing user default values across app launches.
It’s an API used for persisting sensitive data locally, such as passwords and in-app purchase statuses.
Atlas Device SDK is a fast, reactive, and scalable alternative to SQLite that makes storing, syncing, and querying data simple for modern mobile applications.
Like many projects targeting other platforms, creating an app for iOS often requires a database. This article has helped inform you on your choices for the best database for iOS. This has included what to consider when choosing an iOS database, the different types of databases available, different hosting options, and why you might consider object-oriented databases such as the one provided by Atlas Device SDK.
Atlas Device SDK has many SDK's available, including the Realm Swift SDK, so you can get started using it today.
Swift is Apple’s proprietary general-purpose programming language, developed as a successor to Objective-C. It’s used to create projects ranging from mobile and desktop apps to cloud hosted apps.
It adds some improvements over Objective-C such as type inference, type safety, performance improvements, and a much more concise language, requiring fewer lines of code.
Because Swift, like Objective-C, was also developed by Apple for their platforms, it gives access to the Foundation framework, providing access to some useful native features that play a role in data persistence:
UserDefaults:This gives the ability to store user- or application-specific default information, such as preferred playback speed or language.
Keychain:This is where secure data is stored, such as passwords and certificates, and will be well-known to iOS developers due to its role in provisioning devices and applications, and for development.
We will discuss some other examples of iOS data persistence that work well with Swift when we discuss database options later in the article.
The terms Atlas Device SDK and MongoDB are sometimes used interchangeably, which can lead to confusion and people asking if Atlas Device SDK and MongoDB are the same. The following list will explain what each product or term means and how they connect to attempt to remove any ambiguity:
MongoDB
MongoDB is the name of the company that has developed many of the products discussed in this article. MongoDB started out by creating their core database product that could be installed locally or in data centers. It then evolved to have MongoDB Atlas, the database-as-a-service in the cloud. MongoDB Atlas today is an application data platform with a wide variety of features beyond just the database.
MongoDB acquired Atlas Device SDK and has evolved it to include a device-to-cloud synchronization service that syncs back to MongoDB Atlas.
Atlas Device SDK
Atlas Device SDK is an open source, fast, scalable alternative to CoreData and SQLite that makes storing, syncing, and querying data simple for modern iOS applications.
