使用前检查API对象列表是否存在

Question

///我正在从API获取项目列表。但是，并非所有项目都有图像。我在仅获取“媒体”对象方面遇到了挑战；

    // response 

     factory Item.fromJson(Map<String, dynamic> json) {
        return new Posts(
          name: json['package']['description'].toString(),
          image:  json['package']['image']['src'].toString(),

        );

/// API响应

    {
        "code": 200,
        "message": "OK",
        "payload": {
            "items": [
                {


                    "package": {
                        "media": [

//可用媒体

                            {
                                "name": "2176AE9DA4142BD8-F79395896F3F0C698D01D504EA8644C9.jpeg",
                                "original_name": "a326702d-76da-4969-8369-baec0873d69a6987818660473624852.jpg",
                                "size": 1377517,
                                "src": "2176AE9DA4142BD8-F79395896F3F0C698D01D504EA8644C9.jpeg",
                                "mime_type": "image/jpeg",
                                "id": 228,
                                "created_at": "2019-03-19T10:23:25+00:00",
                                "updated_at": "2019-03-19T10:23:25+00:00"
                            }
                        ]
                    },
                    "id": 227
                },

//对象没有媒体

                {
                    "id": 225
                },
                }
                }