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# UIConfigurationStateCustomKey

A key that defines a custom state for a view.

```
struct UIConfigurationStateCustomKey
```

## Overview

Create a custom state key if you want to define a custom state to include in a configuration state.

```swift
// Declare a custom key for a custom isArchived state. 
extension UIConfigurationStateCustomKey {
    static let isArchived = UIConfigurationStateCustomKey("com.my-app.MyCell.isArchived")
}

// Declare an extension on the cell state structure to provide a typed property for this custom state.
extension UICellConfigurationState {
    var isArchived: Bool {
        get { return self[.isArchived] as? Bool ?? false } 
        set { self[.isArchived] = newValue }
    }
}

class MyCell: UICollectionViewCell {
    // This is an existing custom property of the cell.
    var isArchived: Bool { 
        didSet {
            // Ensure that an update is performed whenever this property changes.
            if oldValue != isArchived { 
                setNeedsUpdateConfiguration()
            }
        }
    }

    override var configurationState: UICellConfigurationState {
        // Get the structure from UIKit with the system properties set by calling super. 
        var state = super.configurationState

        // Set the custom property on the state.
        state.isArchived = self.isArchived 
        return state
    }

    override func updateConfiguration(using state: UICellConfigurationState) {
        // Get the default background configuration styling for the current state based on the system states.
        var backgroundConfig = UIBackgroundConfiguration.listPlainCell().updated(for: 
state)

        // Customize the background configuration based on the custom state. 
        if state.isArchived {
            backgroundConfig.visualEffect = UIBlurEffect(style: .systemMaterial) 
        }

        // Apply the background configuration to the cell.
        self.backgroundConfiguration = backgroundConfig 
    }
}
```

## Topics

### Creating a custom state key

[`init(_:)`](/documentation/UIKit/UIConfigurationStateCustomKey/init(_:))

Creates a custom state key.

[`init(rawValue:)`](/documentation/UIKit/UIConfigurationStateCustomKey/init(rawValue:))

Creates a custom state key with the specified raw value.


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