messageモデルとuserモデルのアソシエーションができない

 前提・実現したいこと

messageモデルとuserモデルのアソシエーションで、messageに紐づくユーザーの名前を書き出したい

 発生している問題・エラーメッセージ

user.nameが定義されていないと出てしまう

Showing /Users/ryousuke/projects/chat-space/app/views/messages/_message.html.haml
undefined method `name' for 3707:Fixnum
Trace of template inclusion: app/views/messages/index.html.haml

 該当のソースコード

//eachで変数を定義
   .right-content__messages.clearfix
    .right-content__messages__container
     .right-content__messages__box
      -@messages.each do |message|　←変数定義
       = render partial:"message", locals:{message: message}

//部分テンプレで切り出し
.right-content__messages__box
 .right-content__messages__box__username
　%h4 #{message.user_id.name}←問題の箇所
 .right-content__messages__box__time
  %p #{message.created_at}
 .right-content__messages__box__content
  %p #{message.content}

 試したこと

・アソシエーションの確認
・外部キーの設定
・DB内データの有無確認

 補足情報（FW/ツールのバージョンなど）

class MessagesController < ApplicationController
  def index
    @groups = current_user.groups
    @group = Group.find(1)
    @messages =  Message.where(group_id: params[:group_id]).order("created_at ASC")
  end
end

class Message < ApplicationRecord
  belongs_to :user
  belongs_to :group
end

class User < ApplicationRecord
  # Include default devise modules. Others available are:
  # :confirmable, :lockable, :timeoutable and :omniauthable
  devise :database_authenticatable, :registerable,
         :recoverable, :rememberable, :trackable, :validatable

  has_many :messages
  has_many :group_users
  has_many :groups, through: :group_users
end

ActiveRecord::Schema.define(version: 20180507143441) do

  create_table "group_users", force: :cascade, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8" do |t|
    t.integer  "group_id"
    t.integer  "user_id"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
    t.index ["group_id"], name: "index_group_users_on_group_id", using: :btree
    t.index ["user_id"], name: "index_group_users_on_user_id", using: :btree
  end

  create_table "groups", force: :cascade, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8" do |t|
    t.string   "name",       null: false
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
    t.index ["name"], name: "index_groups_on_name", using: :btree
  end

  create_table "messages", force: :cascade, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8" do |t|
    t.datetime "created_at",               null: false
    t.datetime "updated_at",               null: false
    t.text     "content",    limit: 65535, null: false
    t.string   "image"
    t.integer  "user_id",                  null: false
    t.integer  "group_id",                 null: false
    t.index ["group_id"], name: "fk_rails_841b0ae6ac", using: :btree
    t.index ["user_id"], name: "fk_rails_273a25a7a6", using: :btree
  end

  create_table "users", force: :cascade, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8" do |t|
    t.string   "name",                                null: false
    t.string   "email",                  default: "", null: false
    t.string   "encrypted_password",     default: "", null: false
    t.string   "reset_password_token"
    t.datetime "reset_password_sent_at"
    t.datetime "remember_created_at"
    t.integer  "sign_in_count",          default: 0,  null: false
    t.datetime "current_sign_in_at"
    t.datetime "last_sign_in_at"
    t.string   "current_sign_in_ip"
    t.string   "last_sign_in_ip"
    t.datetime "created_at",                          null: false
    t.datetime "updated_at",                          null: false
    t.index ["email"], name: "index_users_on_email", unique: true, using: :btree
    t.index ["reset_password_token"], name: "index_users_on_reset_password_token", unique: true, using: :btree
  end

  add_foreign_key "group_users", "groups"
  add_foreign_key "group_users", "users"
  add_foreign_key "messages", "groups"
  add_foreign_key "messages", "users"
end