compositionAPIの初歩

ここの説明がそもそもわかりやすかった。

vue-composition-api-rfc.netlify.app

そこに書いてあるコードを借りてくると、こんな感じでuse関数(useは実際は何でも良い)を書いて、

function useCreateFolder (openFolder) {
  // originally data properties
  const showNewFolder = ref(false)
  const newFolderName = ref('')

  // originally computed property
  const newFolderValid = computed(() => isValidMultiName(newFolderName.value))

  // originally a method
  async function createFolder () {
    if (!newFolderValid.value) return
    const result = await mutate({
      mutation: FOLDER_CREATE,
      variables: {
        name: newFolderName.value
      }
    })
    openFolder(result.data.folderCreate.path)
    newFolderName.value = ''
    showNewFolder.value = false
  }

  return {
    showNewFolder,
    newFolderName,
    newFolderValid,
    createFolder
  }
}

そういう関数達を用意して

export default {
  setup() { // ...
  }
}

function useCurrentFolderData(networkState) { // ...
}

function useFolderNavigation({ networkState, currentFolderData }) { // ...
}

function useFavoriteFolder(currentFolderData) { // ...
}

function useHiddenFolders() { // ...
}

function useCreateFolder(openFolder) { // ...
}

setup関数でこれらをcompositして使う。

export default {
  setup () {
    // Network
    const { networkState } = useNetworkState()

    // Folder
    const { folders, currentFolderData } = useCurrentFolderData(networkState)
    const folderNavigation = useFolderNavigation({ networkState, currentFolderData })
    const { favoriteFolders, toggleFavorite } = useFavoriteFolders(currentFolderData)
    const { showHiddenFolders } = useHiddenFolders()
    const createFolder = useCreateFolder(folderNavigation.openFolder)

    // Current working directory
    resetCwdOnLeave()
    const { updateOnCwdChanged } = useCwdUtils()

    // Utils
    const { slicePath } = usePathUtils()

    return {
      networkState,
      folders,
      currentFolderData,
      folderNavigation,
      favoriteFolders,
      toggleFavorite,
      showHiddenFolders,
      createFolder,
      updateOnCwdChanged,
      slicePath
    }
  }
}

refは値のリアクティブ化で、reactiveはオブジェクトの場合と思っておくことにする。