Скачать или смотреть Mastering the Protocol and Delegate Pattern in Swift: Troubleshooting Tips for iOS Developers

Dive into effective solutions for protocol and delegate issues in Swift, and learn how to troubleshoot and fix common mistakes.
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This video is based on the question https://stackoverflow.com/q/63203423/ asked by the user 'multiverse' ( https://stackoverflow.com/u/3151281/ ) and on the answer https://stackoverflow.com/a/63203464/ provided by the user 'Shehata Gamal' ( https://stackoverflow.com/u/5820010/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Mastering the Protocol and Delegate Pattern in Swift: Troubleshooting Tips for iOS Developers

In the realm of iOS development using Swift, the protocol and delegate pattern is a fundamental concept that allows communication between objects. However, many developers encounter issues where this pattern doesn’t work as intended. One such common problem arises when the delegate method isn’t being called, leading to confusion and frustration.

In this post, we'll breakdown the problem, and explore a detailed solution to ensure your delegate methods are called successfully.

Understanding the Problem

Imagine you have a ratings window in your application, allowing users to select and send feedback. You implement the protocol and delegate pattern, but find that your delegate method is never called. Let’s take a look at the situation:

You have a RatingsViewController that presents a ratings interface through a RatingsView. When a user taps a button in the RatingsView, you’re expecting a method defineTheratings(_:) defined in your RatingsPresentation protocol to be executed.

The Current Code Snippet

Here is the relevant part of the code where things start to go wrong:

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

The code above demonstrates that while the view is being added to the main view, a new instance of RatingsView (stored in vc) is created, and the delegate is set to self. However, this instance, vc, is never displayed anywhere. Instead, we're adding rates to the view, which doesn't have the delegate set up.

Solution Steps

To resolve this issue, you need to make a simple adjustment to how you are managing your RatingsView instance. Follow these steps:

1. Remove the Unused Instance

First, you need to remove the instantiation of vc since it will not be used:

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

2. Correctly Set the Delegate

Next, you must set the delegate for the already defined rates instance. Modify the viewDidLoad method as follows:

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

Revised Code

Here's how your updated viewDidLoad method should look:

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

Conclusion

By following these simple adjustments, you should ensure that when a user taps a button in the RatingsView, the delegate method defineTheratings(_:) is correctly triggered. Always remember to set the delegate for the instance that is actually being used in your view hierarchy.

In summary, the protocol and delegate pattern is powerful when implemented correctly, and troubleshooting issues like this can make a significant difference in your app's functionality. Happy coding!