举例：文章--分类

controller/Article.php

<?php
namespace app\admin\controller;
use think\Controller;
use think\Loader;
use app\admin\model\Article as ArticleModle;

/**
 * Description of Article
 *
 * @author Ivan
 */
class Article extends Controller {

    public function lst() {
//        $list = db('article')->alias('a')->join('cate c' ,'c.id=a.cateid')->field('a.*,c.catename')->order('id')->paginate(4);
        $list = ArticleModle::paginate(4);
        $this->assign('list', $list);
        return $this->fetch();
    }
}

model/Article.php

<?php
namespace app\admin\model;
use think\Model;
/**
 * Description of Article
 *
 * @author Ivan
 */
class Article extends Model
{
    public function cate()
    {
        return $this->belongsTo('cate','cateid');
    }
}

article/lst.htm

<tbody>
    {volist name='list' id='vo'}
    <tr>
        <td align="center">{$vo.id}</td>
        <td align="center">{$vo.title}</td>
        <td align="center">{$vo.author}</td>
        <td align="left">{$vo.desc}</td>
        <td align="center">{$vo.keywords}</td>
        <td class="text-center">
            {if condition="$vo['pic'] neq '' "}
            <img src="__IMG__.{$vo.pic}" height='50'/>
            {else /}
            暂无图片
            {/if}
        </td>
        <td align="center">{$vo.click}</td>
        <td align="center">
            {if condition = "$vo['state'] eq '1'  "}
                已推荐
            {else /}
                未推荐
            {/if}
        </td>
        <td align="center">{$vo.time}</td>
        <td align="center">{$vo.cate.catename}</td>
        <--只有这个字段是cate表里的，即外部关联表所以写法不一样-->
        <td align="center">
            <a href="{:url('edit',array('id'=>$vo['id']))}" class="btn btn-primary btn-sm shiny">
                <i class="fa fa-edit"></i> 编辑
            </a>
            {if condition="$vo.id neq '0'"}
            <a href="{:url('del',array('id'=>$vo['id']))}" onClick="warning('确实要删除吗')" class="btn btn-danger btn-sm shiny">
                <i class="fa fa-trash-o"></i> 删除
            </a>
            {/if}
        </td>
    </tr>
    {/volist}
</tbody>

以上还不够，还需要创建,model/Cate.php 空的就可以

namespace app\admin\model;
use think\Model;
/**
 * Description of Article
 *
 * @author Ivan
 */
class Cate extends Model
{

}

提示类不存在，要么没引入，要么没创建，这个类包括controller和model

提示属性不存在，就是view层的问题 当然要看哪个是主表，那个是关联表