postComments = (id, comments) => {
    const existingComments =
      this.state.list.find(post => post.id === id).postcomments || []
    axios
      .patch(`http://localhost:8080/posts/${id}`, {
        postcomments: [comments, ...existingComments],
      })
      .then(result => {
        // https://stackoverflow.com/a/35206193
        const foundIndex = this.state.list.findIndex(post => post.id === id)
        const list = [...this.state.list]
        list[foundIndex] = result.data
        this.setState({ list })
      })
  }