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# callAsFunction(contentType:)

Presents a new document window.

```
@MainActor @preconcurrency func callAsFunction(contentType: UTType)
```

## Parameters

`contentType`

The content type of the document.

## Discussion

Don’t call this method directly. SwiftUI calls it when you
call the [`newDocument`](/documentation/SwiftUI/EnvironmentValues/newDocument) action:

```
newDocument(contentType: .todoList)

 extension UTType {
     static let todoList = UTType(exportedAs: "com.myApp.todoList")
 }
```

> Important: If your app declares custom uniform type identifiers,
> include corresponding entries in the app’s `Info.plist` file.
> For more information, see <doc://com.apple.documentation/documentation/UniformTypeIdentifiers/defining-file-and-data-types-for-your-app>.
> Also, remember to specify the supported Document types in the
> `Info.plist` file as well.

For information about how Swift uses the `callAsFunction()` method to
simplify call site syntax, see
[Methods with Special Names](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#ID622)
in *The Swift Programming Language*.

---

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