<!--
{
  "availability" : [
    "iOS: 16.0.0 -",
    "iPadOS: 16.0.0 -",
    "macCatalyst: 16.0.0 -",
    "macOS: 13.0.0 -",
    "tvOS: 16.0.0 -",
    "visionOS: 1.0.0 -",
    "watchOS: 9.0.0 -"
  ],
  "documentType" : "symbol",
  "framework" : "Swift",
  "identifier" : "/documentation/Swift/String/LocalizationValue/Placeholder/double",
  "metadataVersion" : "0.1.0",
  "role" : "Case",
  "symbol" : {
    "kind" : "Case",
    "modules" : [
      "Swift"
    ],
    "preciseIdentifier" : "s:SS10FoundationE17LocalizationValueV11PlaceholderO6doubleyA2EmF"
  },
  "title" : "String.LocalizationValue.Placeholder.double"
}
-->

# String.LocalizationValue.Placeholder.double

The double-precision floating-point type, as used for replacement values with the localized string placeholder syntax.

```
case double
```

## Discussion

To insert a `double` into a placeholder, use the syntax `\(placeholder: .double)`.

The various `String(localized:)` initializers apply a locale-appropriate `FormatStyle` to the numeric value, based on the `locale:` parameter or the `LocalizedStringResource`.

---

Copyright &copy; 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)