---
title: String.LocalizationValue.Placeholder.double
framework: swift
role: symbol
role_heading: Case
path: swift/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.

## Declaration

```swift
case double
```

## Discussion

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.

## See Also

### Placeholder types

- [String.LocalizationValue.Placeholder.int](swift/string/localizationvalue/placeholder/int.md)
- [String.LocalizationValue.Placeholder.uint](swift/string/localizationvalue/placeholder/uint.md)
- [String.LocalizationValue.Placeholder.float](swift/string/localizationvalue/placeholder/float.md)
- [String.LocalizationValue.Placeholder.object](swift/string/localizationvalue/placeholder/object.md)