Passing data between view controllers

📝 Passing Data Between View Controllers - A Beginner's Guide

Are you new to iOS development and struggling with passing data between view controllers? Don't worry, you're not alone! In this guide, we'll walk you through the common issues and provide easy solutions to help you overcome this hurdle.

🧩 Understanding the MVC Paradigm

Before we dive into passing data between view controllers, let's quickly revisit the Model-View-Controller (MVC) paradigm. MVC is a design pattern that separates an application's data (Model), user interface (View), and the logic that controls the interaction between the two (Controller).

In your case, the data entry form view acts as the View, the table view with multiple selections acts as another View, and the logic that handles data transfer between these two views is represented by the Controller.

💡 The Challenge: Transferring Data Across Views

Your challenge is to transfer the selected products from the table view to the data entry form view for further processing. Here are some common approaches to solve this problem:

1. Using Delegation

Delegation is a simple and effective way to pass data between view controllers. Define a protocol in the table view controller that allows the data entry form view controller to become its delegate. When a product is selected, call the delegate method to pass the selected data to the data entry form view controller. Here's a code snippet to help you visualize the process:

// In the TableViewController
protocol TableViewControllerDelegate: AnyObject {
    func didSelectProducts(_ selectedProducts: [Product])
}

class TableViewController: UITableViewController {
    weak var delegate: TableViewControllerDelegate?
    
    // ...
    
    func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
        let selectedProduct = products[indexPath.row]
        delegate?.didSelectProducts([selectedProduct])
    }
}

// In the DataEntryFormViewController
extension DataEntryFormViewController: TableViewControllerDelegate {
     func didSelectProducts(_ selectedProducts: [Product]) {
         // Handle the selected products here
     }
}

2. Using Callback Closures

If you prefer a more lightweight approach, you can utilize callback closures. Declare a closure property in the table view controller and pass it to the data entry form view controller. When a product is selected, invoke the closure with the selected data. Here's an example:

// In the TableViewController
class TableViewController: UITableViewController {
    var didSelectProducts: (([Product]) -> Void)?
    
    // ...
    
    func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
        let selectedProduct = products[indexPath.row]
        didSelectProducts?([selectedProduct])
    }
}

// In the DataEntryFormViewController
class DataEntryFormViewController: UIViewController {
    // ...
    
    func presentTableView() {
        let tableViewController = TableViewController()
        tableViewController.didSelectProducts = { [weak self] selectedProducts in
            // Handle the selected products here
        }
        present(tableViewController, animated: true, completion: nil)
    }
}

3. Using a Shared Data Model

Another approach is to create a shared data model, where both view controllers can access and modify the same instance of the data model. The data model can be a singleton or stored in an appropriate object, such as an app delegate or a dedicated data manager. However, it's worth noting that excessive use of singletons can make your code complex and harder to maintain.

🌟 Choose the Right Solution

Now that you have a few possible solutions, consider the specifics of your app and decide which approach best suits your needs. Consider factors such as the complexity of your data, the relationship between the view controllers, and the scalability of your app.

🙌 Engage and Share Your Experience

We hope this guide has shed some light on the process of passing data between view controllers. If you found it helpful, don't forget to share it with other iOS developers who might also benefit from it. Have any other questions or facing a different challenge? Let us know in the comments below! Happy coding! 👩‍💻💻👨‍💻

*[UITableViewController]: User Interface Table View Controller