编程这一路

当使用前后端分离，并且前端后端域名不统一时，我遇到了跨域的问题

Access to XMLHttpRequest at http://localhost/api/login from origin http://localhost:8010 has been blocked by CORS policy: Response to preflight request doesnt pass access control check: NoAccess-Control-Allow-Origin header is present on the requested resource.```

Access to XMLHttpRequest at http://localhost/api/login from origin http://localhost:8010 has been blocked by CORS policy: Request header field content-type is not allowed by Access-Control-Allow-Headers in preflight response.

我们只需要在返回的 response 中添加 header就可以了

首先我们创建一个 Filter 用来批量在生成的 response 中添加 headers

App\Filters\Api.php
<?php
namespace App\Filters;

use CodeIgniter\Filters\FilterInterface;
use CodeIgniter\HTTP\RequestInterface;
use CodeIgniter\HTTP\ResponseInterface;

class Api implements FilterInterface
{
    public function before(RequestInterface $requset)
    {

    }

    public function after(RequestInterface $request, ResponseInterface $response)
    {
        $response->setHeader(Access-Control-Allow-Origin, *);
        $response->setHeader(Access-Control-Allow-Headers, Content-Type);
        return $response;
    }
}

接下来我们将注册并配置 App\Filters\Api::class, 编辑配置文件 App\Config\Filters.php

...
    public $aliases = [
        csrf     => \CodeIgniter\Filters\CSRF::class,
        toolbar  => \CodeIgniter\Filters\DebugToolbar::class,
        honeypot => \CodeIgniter\Filters\Honeypot::class,
        api => \App\Filters\Api::class,  //注册 Filter
    ];
...

配置该 filter 对哪些 uri 生效

public $filters = [
        api => [
            after =>[
                api/*,
            ]
        ]
    ];

至此，在每个路径为 api/* 的请求返回前，就会执行 after 中的代码，添加 headers