不能从一对一的多态实现中检索数据

Question

我有一张书表和一张图像表，将来我也会有一个博客表格。这就是为什么我想在图书、博客和图像表之间创建一个多态关系的原因。但我的问题是，当我尝试从视图home.blade.php与@foreach的关系中检索图书图像url的数据时，我得到了以下信息：

Call to a member function getImage() on null (View: F:\xampp\htdocs\BookReader\resources\views\Main_pages\includes\Home\new_product.blade.php)

守则如下：

home.blade.php

@extends('Main_pages.app')
@section('title','Home')
@section('content')
    @include('Main_pages.includes.Home.new_product')

    @include('Main_pages.includes.Home.testimonial')

    @include('Main_pages.includes.Home.popular_products')

    @include('Main_pages.includes.Home.news_letter')

    @include('Main_pages.includes.Home.blogs')

    @include('Main_pages.includes.Home.quick_view')
@endsection

new_product.blade.php

<section class="wn__product__area brown--color pt--80  pb--30">
<div class="container">
    <div class="row">
        <div class="col-lg-12">
            <div class="section__title text-center">
                <h2 class="title__be--2">New <span class="color--theme">Products</span></h2>
                <p>There are many variations of passages of Lorem Ipsum available, but the majority have suffered lebmid alteration in some ledmid form</p>
            </div>
        </div>
    </div>
    <!-- Start Single Tab Content -->
    <div class="furniture--4 border--round arrows_style owl-carousel owl-theme row mt--50">
        @foreach($new_books as $book)
        <!-- Start Single Product -->}}
        <div class="product product__style--3">
            <div class="col-lg-3 col-md-4 col-sm-6 col-12">
                <div class="product__thumb">
                    <a class="first__img" href="single-product.html"><img src="{{$book->image->getImage()}}" alt="product image"></a>
                    <div class="hot__box">
                        <span class="hot-label">BEST SALLER</span>
                    </div>
                </div>
                <div class="product__content content--center">
                    <h4><a href="single-product.html">{{$book->title()}}</a></h4>
                    <ul class="prize d-flex">
                        <li>$35.00</li>--}}
                        <li class="old_prize">$35.00</li>
                    </ul>
                    <div class="action">
                        <div class="actions_inner">
                            <ul class="add_to_links">
                                <li><a class="cart" href="cart.html"><i class="bi bi-shopping-bag4"></i></a></li>
                                <li><a class="wishlist" href="wishlist.html"><i class="bi bi-shopping-cart-full"></i></a></li>
                                <li><a class="compare" href="#"><i class="bi bi-heart-beat"></i></a></li>
                                <li><a data-toggle="modal" title="Quick View" class="quickview modal-view detail-link" href="#productmodal"><i class="bi bi-search"></i></a></li>
                            </ul>
                        </div>
                    </div>
                    <div class="product__hover--content">
                        <ul class="rating d-flex">
                            <li class="on"><i class="fa fa-star-o"></i></li>
                            <li class="on"><i class="fa fa-star-o"></i></li>
                            <li class="on"><i class="fa fa-star-o"></i></li>
                            <li><i class="fa fa-star-o"></i></li>
                            <li><i class="fa fa-star-o"></i></li>
                        </ul>
                    </div>
                </div>
            </div>
        </div>
        <!-- Start Single Product -->
        @endforeach
    </div>
    <!-- End Single Tab Content -->
</div>

图像迁移

public function up()
{
    Schema::create('images', function (Blueprint $table) {
        $table->id();
        $table->text('url');
        $table->unsignedBigInteger('imageable_id');
        $table->text('imageable_type');
        $table->timestamps();
    });
}

图书迁移

public function up()
{
    Schema::create('books', function (Blueprint $table) {
        $table->id();
        $table->string('book_title');
        $table->string('book_author');
        $table->text('book_description');
        $table->timestamps();
    });
}

图像模型

class Image extends Model
{
    public function imageable(){
        return $this->morphTo();
   }
    public function getImage(){
        return $this->url;
   }
}

图书模型

class Book extends Model
{
    public function image(){
        return $this->morphOne(Image::class,'imageable');
    }
    public function title(){
        return $this->book_title;
    }
    public function author(){
        return $this->book_author;
    }
    public function desc(){
        return $this->book_description;
    }
}

HomeController

class HomeController extends Controller
{
    public function view(){
        $new_books = Book::latest()->get();

        return view('Main_pages.Pages.home',['new_books'=>$new_books]);
    }
}

Answer 1

这很明显。有一本没有图像的书。将img代码更改为：

@isset ($book->image)
    <img src="{{$book->image->getImage()}}" alt="product image">
@endisset

或者使用optional method和Null Coalesce Operator获得默认图像：

<img src="{{optional($book->image)->getImage() ?? 'default_image_path.png'}}" alt="product image">

或者这个：

@if (isset($book->image))
    <img src="{{$book->image->getImage()}}" alt="product image">
@else
    <img src="default_image_path.png" alt="product image">
@endif

希望这能帮到你。