---
title: "appendInterpolation(yearForWeekOfYear:)"
framework: foundation
role: symbol
role_heading: Instance Method
path: "foundation/date/formatstring/stringinterpolation/appendinterpolation(yearforweekofyear:)"
---

# appendInterpolation(yearForWeekOfYear:)

## Declaration

```swift
mutating func appendInterpolation(yearForWeekOfYear: Date.FormatStyle.Symbol.YearForWeekOfYear)
```