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# parameterString

The parameter string conforming to RFC 1808. (read-only)

```
var parameterString: String? { get }
```

## Discussion

This property contains the parameter string. Any percent-encoded characters are not unescaped. If the receiver does not conform to RFC 1808, this property contains `nil`.  For example, in the URL `file:///path/to/file;foo`, the parameter string is `foo`.

This property should not be confused with the [`query`](/documentation/Foundation/NSURL/query) property, which also often contains a string of parameters.

---

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