Document入力

show.blade.php
DocumentsController@storeにpostする。

<form method="post" action="{{ action('DocumentsController@store', $article) }}">
		{{ csrf_field()}}
	<p>
		<input type="text" name="login_id" placeholder="iphone/android" value="{{ old('mobile') }}">
		@if($errors->has('mobile'))
		<span class="error">{{ $errors->first('mobile') }}</span>
		@endif
	</p>
	<p>
		<input type="text" name="role" placeholder="配信日" value="{{ old('published_at') }}">
		@if($errors->has('published_at'))
		<span class="error">{{ $errors->first('published_at') }}</span>
		@endif
	</p>
	<p>
		<input type="text" name="name" placeholder="原稿" value="{{ old('body') }}">
		@if($errors->has('body'))
		<span class="error">{{ $errors->first('body') }}</span>
		@endif
	</p>
	<p>
		<input type="submit" value="登録">
	</p>
	</form>

routing
DocumentsController@storeを/articles/{article}/documentsと設定する。

Route::get('/', 'ArticlesController@index');
Route::get('/articles/create', 'ArticlesController@create');
Route::get('/articles/{id}', 'ArticlesController@show')->where('post','[0-9]+');
Route::post('/articles', 'ArticlesController@store');
Route::get('/articles/{id}/edit', 'ArticlesController@edit');
Route::patch('/articles/{article}', 'ArticlesController@update');
Route::delete('/articles/{article}', 'ArticlesController@destroy');
Route::post('/articles/{article}/documents', 'DocuumentsController@store');

mysqlにも値が入りました。
mysql> select * from documents;
+—-+————+——–+————–+——–+———————+———————+
| id | article_id | mobile | published_at | body | created_at | updated_at |
+—-+————+——–+————–+——–+———————+———————+
| 1 | 10 | iphone | 9/12 | aaaaaa | 2018-09-23 08:46:45 | 2018-09-23 08:46:45 |
+—-+————+——–+————–+——–+———————+———————+
1 row in set (0.00 sec)