Ruby on rails Api:：SessionController#create中的NoMethodError

我在rails 5 api中的会话控制器中不断遇到此错误：

undefined method `[]' for nil:NilClass

老实说，我不确定我做错了什么。以下是会话控制器的代码（第8行出现错误）：

---

如果有人能帮我找到解决这个错误的方法，我将不胜感激。谈到JSON api，我是个新手。

我打赌params[：session]为零。这就是为什么链接哈希键是个坏主意

另请参见散列#挖掘

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（这对我来说是新闻！）

@User

不是查找ActiveRecord对象的有效方法。它应该是模型的名称，大写，然后是find方法

将

@user=@user…

更改为

@user=user。通过…

查找，您应该能够正确完成查找

我喜欢做的一件事是在有问题的行上方放置一个byebug，然后在终端中建立“逐点”查询，看看我是否能找到哪里出错了。它还可以让您查看参数内部，以确保其中存在某些内容

module Api
class SessionsController < ApplicationController

def new
end

def create
  # The error occurs on this line
  @user = @User.find_by(email: params[:session][:email].downcase)
    if user && user.authenticate(params[:session][:password])
      render :text => user.access_token, status: 200
    else
      render text: "Email and password combination are invalid", status: 422
    end
end


def verify_access_token
  user = User.find_by(access_token: params[:session][:access_token])
    if user
      render text: "verified", status: 200
    else
      render text: "Token failed verification", status: 422
    end
  end

 end
end

module SessionsHelper
# Logs in the given user.
def log_in(user)
session[:user_id] = user.id
end

# Remembers a user in a persistent session.
# signed creates an encrypted cookie so that's why we use it.
def remember(user)
  user.remember
  cookies.permanent.signed[:user_id] = user.id
  cookies.permanent[:remember_token] = user.remember_token
end

# Returns true if the given user is the current user.
def current_user?(user)
  user == current_user
end

# Returns the current logged-in user (if any).
def current_user
  if (user_id = session[:user_id])
   @current_user ||= User.find_by(id: user_id)
  elsif (user_id = cookies.signed[:user_id])
    user = User.find_by(id: user_id)
    if user && user.authenticated?(cookies[:remember_token])
    log_in user
    @current_user = user
   end
 end
end

# Returns true if the user is logged in, false otherwise.
def logged_in?
 !current_user.nil?
end

# Forgets a persistent session.
def forget(user)
  user.forget
  cookies.delete(:user_id)
  cookies.delete(:remember_token)
end

def log_out
  forget(current_user)
  session.delete(:user_id)
  @current_user = nil
end

# Redirects to stored location (or to the default).
def redirect_back_or(default)
  redirect_to(session[:forwarding_url] || default)
  session.delete(:forwarding_url)
end

# Stores the URL trying to be accessed.
def store_location
  session[:forwarding_url] = request.url if request.get?
end