---
title: "buildPartialBlock(first:)"
framework: regexbuilder
role: symbol
role_heading: Type Method
path: "regexbuilder/alternationbuilder/buildpartialblock(first:)-520tx"
---

# buildPartialBlock(first:)

## Declaration

```swift
static func buildPartialBlock<R, W, C1>(first regex: R) -> ChoiceOf<(W, C1?)> where R : RegexComponent, R.RegexOutput == (W, C1)
```