How to Pass an Array to Another View Controller in iOS Using Swift

Learn effective ways to pass data between view controllers in iOS using Swift. Explore how to manage data efficiently, especially for arrays, and optimize your application performance.
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This video is based on the question https://stackoverflow.com/q/67333724/ asked by the user 'kacper99' ( https://stackoverflow.com/u/14887685/ ) and on the answer https://stackoverflow.com/a/67334132/ provided by the user 'seto nugroho' ( https://stackoverflow.com/u/5553151/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Passing an Array to Another View Controller in iOS Using Swift

When developing an iOS app, it's common to have multiple view controllers that need to share data. A typical scenario involves passing an array of values, such as workout names, from one view controller to another within a Tab Bar Controller. However, a common challenge developers face is how to effectively pass this data when the view controllers are not connected via segues. This article explores a practical solution to pass an array of values efficiently without relying on long waits for database retrievals.

The Challenge: Passing Data Between View Controllers

In our scenario, you have a HomeTableViewController that contains an array of workout names that you want to send to a CalendarViewController. While it's possible to directly instantiate a new view controller to pass data, this approach will result in an empty array since the new instance does not retain the data from the original instance. This leads to confusion when trying to access the workout names in the second view controller.

Example of the Situation

Your first view controller looks something like this:

[[See Video to Reveal this Text or Code Snippet]]

However, in your CalendarViewController, you mistakenly create a new instance of HomeTableViewController and attempt to access its workoutsName:

[[See Video to Reveal this Text or Code Snippet]]

As you can see, the data remains empty because homeVC is a brand new instance, devoid of the data you originally populated.

A More Effective Solution: Using UserDefaults

Given the need to access this data across multiple view controllers and the absence of a direct segue, a better approach would be to utilize UserDefaults. This method allows you to persistently store simple data types like arrays and easily retrieve them when needed.

Step 1: Save Data to UserDefaults

In your HomeTableViewController, update your sendDataToCalendar function to save the workoutsName array using UserDefaults:

[[See Video to Reveal this Text or Code Snippet]]

Step 2: Retrieve Data from UserDefaults

Next, in your CalendarViewController, you can create a function to retrieve this saved data:

[[See Video to Reveal this Text or Code Snippet]]

By employing UserDefaults, you ensure that data can be shared across view controllers and even persist across app launches, enhancing the overall user experience.

Benefits of Using UserDefaults

Simplicity: UserDefaults offers a straightforward way to store simple data types.

Persistence: Data saved in UserDefaults can be accessed even after the app is closed and reopened.

Versatility: Easily manage data that will be shared across different parts of your application.

Conclusion

In conclusion, effectively passing an array between view controllers in iOS doesn't have to be cumbersome. Rather than trying to link instances directly, leverage the capabilities of UserDefaults to handle data storage and retrieval. This not only streamlines your code but also provides a more efficient method for managing persistent data across your application's lifecycle.

Feel free to implement these methods and ensure smooth data transitions between your view controllers for a better user experience!

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