How to fix "This decoder will only decode classes that adopt NSSecureCoding. Class 'UIImageView' does not adopt it."

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05-10-2024

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"This decoder will only decode classes that adopt NSSecureCoding": A Simple Fix for Your iOS App

Have you ever encountered the cryptic error "This decoder will only decode classes that adopt NSSecureCoding. Class 'UIImageView' does not adopt it" while working on your iOS app? This error often pops up when you're attempting to decode data using NSKeyedArchiver or NSKeyedUnarchiver, and it's particularly frustrating when you're trying to work with seemingly simple objects like UIImageView.

Let's break down the issue and provide a simple fix.

Understanding the Error

At its core, this error message indicates that you're trying to decode data representing an object that doesn't adhere to the NSSecureCoding protocol. This protocol ensures that your objects can be reliably serialized and deserialized, preventing potential security vulnerabilities and data corruption.

Think of it this way: When you encode an object, you're basically turning it into a stream of bytes. NSSecureCoding acts as a safeguard, making sure that these bytes can be safely reconstructed into the original object upon decoding.

The Problem: UIImageView and Secure Coding

The problem is that UIImageView itself doesn't implement the NSSecureCoding protocol. You can't directly encode and decode a UIImageView object using NSKeyedArchiver and NSKeyedUnarchiver without addressing this.

A Simple Fix: Encoding and Decoding the Relevant Data

The solution lies in understanding that you don't need to encode and decode the entire UIImageView object directly. Instead, focus on encoding and decoding the essential data associated with it, such as:

1. Image: The actual image data displayed by the UIImageView can be encoded and decoded using NSData or UIImagePNGRepresentation.
2. Frame: The position and size of the UIImageView on the screen can be encoded and decoded using CGRect.
3. Content Mode: The way the image is scaled within the UIImageView can be encoded and decoded using UIViewContentMode.

Here's how you can implement this fix:

// Encoding
let image = UIImage(named: "yourImage")! 
let imageData = UIImagePNGRepresentation(image) // Assuming PNG format

let encodedData = NSMutableData()
let archiver = NSKeyedArchiver(forWritingWith: encodedData)

archiver.encode(imageData, forKey: "image") // Encode image data
archiver.encode(imageView.frame, forKey: "frame") // Encode frame 
archiver.encode(imageView.contentMode.rawValue, forKey: "contentMode") // Encode content mode

archiver.finishEncoding()

// Decoding
let decoder = NSKeyedUnarchiver(forReadingWith: encodedData)

let decodedImageData = decoder.decodeObject(forKey: "image") as! Data
let decodedFrame = decoder.decodeCGRect(forKey: "frame")
let decodedContentMode = decoder.decodeInteger(forKey: "contentMode") 

// Create and configure UIImageView with decoded data
let newImageView = UIImageView(frame: decodedFrame)
newImageView.image = UIImage(data: decodedImageData)
newImageView.contentMode = UIView.ContentMode(rawValue: decodedContentMode)!

// Add newImageView to your view hierarchy

Key Points:

• Focus on Data: Don't try to encode and decode complex objects directly. Instead, break down the relevant data and encode/decode it individually.
• Data Types: Use appropriate data types for encoding and decoding (e.g., NSData, CGRect, NSInteger).
• Key Paths: Use meaningful key paths to store and retrieve your encoded data.

Conclusion

By understanding the limitations of NSSecureCoding and focusing on encoding and decoding the relevant data associated with your UIImageView, you can easily overcome the "This decoder will only decode classes that adopt NSSecureCoding" error and create a secure and robust iOS app.

Remember, if you're working with custom classes, it's generally a good practice to implement the NSSecureCoding protocol to ensure your app's data integrity.