如何在 Rails 的 Show 视图中添加「下一页」与「上一页」
用分页的 Gem 可以很容易在 index 的视图中实现分页，可是如何在 show 的视图中也显示分页呢？
一开始用关键词 show next previous 没有搜索到有用的
后来 换了关键词，has_many next previous 就找到几条有用的记录
# post.rb
def previous_post
previous_posts = Post.where [ 'created_at < ?', self.created_at ]
previous_post = previous_posts.find(:all, :order => 'created_at DESC').first
previous_post.nil? ? Post.find(:all, :order => 'created_at DESC').first : previous_post
end
def next_post
next_posts = Post.where [ 'created_at > ?', self.created_at ]
next_post = next_posts.find(:all, :order => 'created_at ASC').first
next_post.nil? ? Post.find(:all, :order => 'created_at ASC').first : next_post
end
方法如下，具体根据情况进行修改，如可将 created_at 换成 id, title 等字段
ref: post.rb
# post_controller.rb
def show
@post = Post.find(params[:id])
@previous = @post.previous_post
@next = @post.next_post
end
<div class="previous"><%= link_to "...#{@previous.title}", post_path(@previous) %></div>
<div class="next"><%= link_to "#{@next.title}...", post_path(@next) %></div>
有时需要处理类似当 post 属于某一分类时的情景
如 post belongs_to :category
可以这样处理
# model/post.rb
belongs_to :category
def next
category.posts.where("time > ?", time).order(:time).first
end
def previous
category.posts.where("time < ?", time).order(time: :desc).first
end
# model/category.rb
has_many :posts
# routes.rb
resources :categories do
resources :posts, shallow: true
end
end
# posts_controller.rb
def show
@category = Category.find_by_id(@post.category_id)
@posts = @category.posts
@previous_post = @post.previous
@next_post = @post.next
end
在另一个实例中，甚至使用了查询语句
def show
@quiz = Quiz.find(params[:quiz_id])
@question = @quiz.questions.find(params[:id])
@previous_question = @quiz.questions.where('quiz_questions.quiz_id = ? and questions.id < ?', @quiz.id, @question.id).order('id DESC').first
@next_question = @quiz.questions.where('quiz_questions.quiz_id = ? and questions.id > ?', @quiz.id, @question.id).order('id ASC').first
end