TodoToggle.alt2.vue

<template>
...
</template>
<script>
...

  methods: {
    updateCache (store, { data: { toggleTodo } }) {
      const id = `TodoItem:${this.id}`
      const fragment = queries.toggleTodoFragment
      const todo = store.readFragment({ fragment, id })
      const data = { ...todo, completed: !todo.completed }
      store.writeData({ data, id })
    }
  }
}
</script>