Rails 中 nil:NilClass 的路由錯誤未定義方法 `<'

Question

如何解決此錯誤：

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我正在嘗試在模型中設置自定義驗證方法，但我得到了

路由錯誤未定義的方法 `<' for nil:NilClass

這是商品型號代碼

# article.rb
class Article < ActiveRecord::Base
    validates_presence_of :category_id, :title, :body, :is_publish, :publish_date, :feature_image_url
    validates_numericality_of :category_id, greater_than: 0
    validates_length_of :title, minimum: 5
    validates_length_of :body, within: 5..200
    validates_uniqueness_of :title

    validate :publish_date_cannot_be_more_than_one_month_from_today
    def publish_date_cannot_be_more_than_one_month_from_today
        if publish_date > (Date.today + 1.month)
            errors.add(:publish_date, "Can't be more than 1 month from today")
        end
    end
end

這是articles_controller.rb 的代碼articles_controller.rb

class ArticlesController < ApplicationController
    def index
        @articles = Article.all
    end
    def new
        @article = Article.new
    end
    def create
        @article = Article.new(article_params)
        if @article.save
            redirect_to articles_path
        else
            render action: "new"
        end
    end
    def show
        @article = Article.find(params[:id])
        @category = Category.find(@article.category_id)
    end
    def edit
        @article = Article.find(params[:id])
    end
    def update
        @article = Article.find(params[:id])
        if @article.update_attributes(article_params)
            redirect_to articles_path
        else
            render action: "new"
        end
    end
    def destroy
        @article = Article.find(params[:id])
        @article.destroy
        redirect_to articles_path       
    end
    a = Article.new

    a.publish_date_cannot_be_more_than_one_month_from_today 
    private

    def article_params
        params[:article].permit(:title, :body, :is_publish, :publish_date, :category_id, :feature_image_url)
    end
end

Answer 1

從您的文章控制器中刪除這兩行。它在您的操作之外

a = Article.new

a.publish_date_cannot_be_more_than_one_month_from_today