search_controller.rb

class SearchController < ApplicationController
  
  def search
    @model = params["search"]["model"]     　　　  #Select model@Assign to model
    @value = params["search"]["value"]     　　　  #Searched string(Here value)To@Assign to value
    @how = params["search"]["how"]　　　　　　　　  #The selected search method how@Assign to how
    @datas = search_for(@how, @model, @value)      #search_Define an instance variable in the argument of for
  end　　　　　　　　　　　　　　　　　　　　　　　　  #@datas will contain the final search results
  
  private

  def match(model, value)                     #def search_Processing when how is match in for
    if model == 'user'                        #Processing when model is user
      User.where(name: value)                 #Where to find a name that exactly matches the value
    elsif model == 'book'　　         
      Book.where(title: value)
    end
  end
  
  def forward(model, value)
    if model == 'User'
      User.where("name LIKE ?", "#{value}%")
    elsif model == 'book'
      Book.where("title LIKE ?", "#{value}%")
    end
  end
  
  def backward(model, value)
    if model == 'user'
      User.where("name LIKE ?", "%#{value}")
    elsif model == 'book'
      Book.where("title LIKE ?", "%#{value}")
    end
  end
  
  def partical(model, value)
    if model == 'user'
      User.where("name LIKE ?", "%#{value}%")
    elsif model == 'book'
      Book.where("title LIKE ?", "%#{value}%")
    end
  end
  
  def search_for(how, model, value)　　　　#The information defined in the search action is included in the argument
    case how                              #The process of searching from the conditional branch of when which is the content of how of the search method
    when 'match'
      match(model, value)                 #In the argument of the search method(model, value)Is defined
    when 'forward'                        #For example, if how is match, proceed to def match processing.
      forward(model, value)
    when 'backward'
      backward(model, value)
    when 'partical'
      partical(model, value)
    end
  end
end

#Prefix match
Model name.where("Column name LIKE?", "value%")
#Backward match
Model name.where("Column name LIKE?", "%value")
#Partial Match
Model name.where("Column name LIKE?", "%value%")

⑤ Edit View page

I will describe it in views / search / search.html.erb

search.html.erb

<div class="container">
  <div class="col-xs-12">
    <% if @model == "user" %>
    <h2>Users search for '<%= @value %>'</h2>
    <table class="table">
        <thead>
            <tr>
                <th></th>
                <th>Name</th>
                <th>Introduction</th>
            </tr>
        </thead>
    <% @datas.each do |user| %>
        <tbody>
            <tr>
                <th>
                    <%= attachment_image_tag(user, :profile_image, :fill, 40, 40, fallback: "no_image.jpg ", size:'40x40') %>
                </th>
                <th>
                    <%= user.name %>
                </th>
                <th>
                    <%= user.introduction %>
                </th>
            </tr>
        </tbody>
    <% end %>
    <% elsif @model == "book" %>
    <h2>Books search for '<%= @value %>'</h2>
    <table class="table">
        <thead>
            <tr>
                <th></th>
                <th>Title</th>
                <th>Opinion</th>
            </tr>
        </thead>
        <% @datas.each do |book| %>
        <tbody>
            <tr>
                <th>
                    <%= attachment_image_tag(book.user, :profile_image, :fill, 40, 40, fallback: "no_image.jpg ", size:'40x40') %>
                </th>
                <th>
                    <%= book.title %>
                </th>
                <th>
                    <%= book.body %>
                </th>
            </tr>
        </tbody>
        <% end %>
    <% end %>
    </table>
  </div>
</div>