检查父记录将来是否有任何带有start_date的子记录，然后停止更新rails

class Parent < ApplicationRecord
  validate :check_child_start_date

  private

  def check_child_start_date
    if children.exists?(start_date: Date.today..)
      errors.add(:base, "Cannot update parent record as it has child records with future start dates.")
    end
  end
end

class Parent < ApplicationRecord
  has_many :children
  # ...
end

class Child < ApplicationRecord
  belongs_to :parent
  # ...
end

class ParentsController < ApplicationController
  def update
    @parent = Parent.find(params[:id])
    if @parent.update(parent_params)
      # update successful
    else
      # update failed
    end
  end

  private

  def parent_params
    params.require(:parent).permit(:attribute1, :attribute2, ...)
  end
end

<%= form_with(model: @parent, url: parent_path(@parent), method: :patch) do |form| %>
  <% if @parent.errors.any? %>
    <div id="error_explanation">
      <h2><%= pluralize(@parent.errors.count, "error") %> prohibited this parent from being updated:</h2>
      <ul>
        <% @parent.errors.full_messages.each do |message| %>
          <li><%= message %></li>
        <% end %>
      </ul>
    </div>
  <% end %>
  <!-- form fields and submit button -->
<% end %>