Yii2框架Users模块登录表单验证码功能失效问题及解决

我在应用的其他表单中实现的验证码字段可正常工作，但在Users模块的登录表单中，验证码功能失效。

相关代码 #

登录表单代码 #

<?= $form->field($user, 'captcha')->widget(\yii\captcha\Captcha::className(), [
    'captchaAction' => 'user/captcha',  // Important, otherwise no image shown.
    'template' => '...',
]); ?>

User模型代码 #

class User extends ActiveRecord implements IdentityInterface
{
    public $captcha;

    public function rules()
    {
        return [
            ...
            /* Modified after the suggestion of Michal Hynčica. */
            /* I tried also 'users/user/captcha'. */
            ['captcha', 'captcha', 'captchaAction' => 'user/captcha'],
        ];
    }
}

UserController的actions()方法 #

public function actions()
{
    return [
        'captcha' => [
            'class' => 'yii\captcha\CaptchaAction',
        ],
    ];
}

UserController的behaviors()方法 #

public function behaviors()
{
   return [
        'access' => [
            'class' => AccessControl::className(),
            'rules' => [
                [
                    'actions' => ['captcha'],
                    'allow' => true,
                ],
            ],
        ]
   ];
}

问题解决方法 #

由于User模型中存在多个场景，需要将captcha字段添加到登录场景中：

public function scenarios()
{
    return [
        ...
        self::SCENARIO_LOGIN => ['name', 'password', 'remember', 'captcha'],
    ];
}

内容的提问来源于stack exchange，提问作者anva