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# encode(_:forKey:)

Encodes an object and associates it with the string key.

```
func encode(_ object: Any?, forKey key: String)
```

## Discussion

Subclasses must override this method to identify multiple encodings of `objv` and encode a reference to `objv` instead. For example, `NSKeyedArchiver` detects duplicate objects and encodes a reference to the original object rather than encode the same object twice.

## See Also

[`decodeObject(forKey:)`](/documentation/Foundation/NSCoder/decodeObject(forKey:))

Decodes and returns a previously-encoded object that was previously encoded with [`encode(_:forKey:)`](/documentation/Foundation/NSCoder/encode(_:forKey:)-1mlmu) or [`encodeConditionalObject(_:forKey:)`](/documentation/Foundation/NSCoder/encodeConditionalObject(_:forKey:)) and associated with the string `key`.


---

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