SE-0289: Result builders中详细说明了结果生成器转换代码的方式。"选择语句"一节介绍了if/else语句如何转换。它给出了以下示例：
请看下面的代码：

if i == 0 {
  "0"
} else if i == 1 {
  "1"
} else {  
  generateFibTree(i)
}

在此模式下，示例代码如下所示：

let vMerged: PartialResult
if i == 0 {
  var firstVar = "0"
  var firstBlock = BuilderType.buildBlock(firstVar)
  vMerged = BuilderType.buildEither(first: firstBlock)
} else if i == 1 {
  var secondVar = "1"
  var secondBlock = BuilderType.buildBlock(secondVar)
  vMerged = BuilderType.buildEither(second:
        BuilderType.buildEither(first: secondBlock))
} else {
  var elseVar = generateFibTree(i)
  var elseBlock = BuilderType.buildBlock(elseVar)
  vMerged = BuilderType.buildEither(second:
        BuilderType.buildEither(second: elseBlock))
}

您还可以阅读转换算法的详细描述，但我认为该示例已经足够清楚，它将只执行if/else语句的一个分支。