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# didChangeValue(forKey:)

Informs the observed object that the value of a given property has changed.

```
func didChangeValue(forKey key: String)
```

## Parameters

`key`

The name of the property that changed.

## Discussion

Use this method when implementing key-value observer compliance manually to inform the observed object that the value at `key` has just changed. Calls to this method are always paired with a matching call to [`willChangeValue(forKey:)`](/documentation/ObjectiveC/NSObject-swift.class/willChangeValue(forKey:)).

### Special Considerations

You rarely need to override this method in subclasses, but if you do, be sure to call `super`.

---

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