为什么我得到未定义的方法“保存”错误？

Question

我的代码是这样的

def footstamp 
    if current_user 
     @user = User.find(params[:id]) 
     @tracking = Tracking.where(:user_id => current_user.id, :target_user_id => @user.id) 

     if @tracking 
      @tracking.accessed_at = Time.now 
      @tracking.save   
     else 
      @tracking = Tracking.new 
      @tracking.user_id = current_user.id 
      @tracking.target_user_id = @user.id 
      @tracking.accessed_at = Time.now 
      @tracking.save   
     end 
    end  
end 

然后我得到这个错误

NoMethodError (undefined method `save' for []:ActiveRecord::Relation): 

Answer 1

用途：

@tracking = Tracking.where(:user_id => current_user.id, :target_user_id => @user.id).first 

Answer 2

您收到此错误，因为你的方法的结果，不返回Tracking ，但是一组Trackings。

要么你引入更多的条件来匹配只有一个Tracking，或者使用first方法或遍历结果，

首先使用：

@tracking = Tracking.where(:user_id => current_user.id, :target_user_id => @user.id).first 

迭代：

Tracking.where(:user_id => current_user.id, :target_user_id => @user.id).each do |tracking| 
     if tracking 
      tracking.accessed_at = Time.now 
      tracking.save   
     else 
      tracking = Tracking.new 
      tracking.user_id = current_user.id 
      tracking.target_user_id = @user.id 
      tracking.accessed_at = Time.now 
      tracking.save   
     end 
end 

Answer 3

优化答案，

def footstamp 
    if current_user 
     @user = User.find(params[:id]) 
     @tracking = Tracking.where(:user_id => current_user.id, :target_user_id => @user.id).first_or_create 
     @tracking.accessed_at = Time.now 
     @tracking.save   
    end  
end 

更有用的方法here