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# NSMapInsertKnownAbsent(_:_:_:)

Inserts a key-value pair into the specified table if the pair had not been previously added.

```
func NSMapInsertKnownAbsent(_ table: NSMapTable<AnyObject, AnyObject>, _ key: UnsafeRawPointer?, _ value: UnsafeRawPointer?)
```

## Discussion

Inserts `key` (which must not be `notAKeyMarker`) and `value` into `table`. Unlike `NSMapInsert`, this function raises `NSInvalidArgumentException` if `table` already includes a key that matches `key`.

`key` is compared with `notAKeyMarker` using pointer comparison; if `key` is identical to `notAKeyMarker`, raises `NSInvalidArgumentException`.

## See Also

[`NSMapInsertIfAbsent`](/documentation/Foundation/NSMapInsertIfAbsent(_:_:_:))

Inserts a key-value pair into the specified table.

[`NSMapRemove`](/documentation/Foundation/NSMapRemove(_:_:))

Removes a key and corresponding value from the specified table.

[`NSMapInsert`](/documentation/Foundation/NSMapInsert(_:_:_:))

Inserts a key-value pair into the specified table.


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