Flutter中GraphQL mutation传递对象数组类型不匹配怎么解决？

第一步：修正Mutation语法错误 #

你当前定义的mutation变量定义里，$merchantId: String! 后面缺少英文逗号，会直接触发语法校验失败，先修正：

String inviteEmployeeMutation = """
    mutation inviteEmployee (
        \$storeId: String!,
        \$merchantId: String!,
        \$employees: [NewEmployeeInput!]! // 建议加上非空校验避免传空报错
    ) {
        invitationEmployee (
            input: {
                storeId: \$storeId
                merchantId: \$merchantId        
                employees: \$employees
            }
        ) {
            nodes {
                id        
                firstName        
                lastName        
                email    
                mobile
            }        
        }
    }                
""";

第二步：正确序列化传递的对象数组 #

之前传递Dart对象实例列表触发类型不匹配，是因为GraphQL客户端只接收纯JSON结构的入参，不需要额外做编码再解码的操作，只要把每个NewEmployeeInput对象调用toJson()转为纯Map即可：
假设你的NewEmployeeInput类定义如下：

class NewEmployeeInput {
  final String firstName;
  final String lastName;
  final String? email;
  final String? mobile;

  NewEmployeeInput({required this.firstName, required this.lastName, this.email, this.mobile});

  Map<String, dynamic> toJson() => {
    "firstName": firstName,
    "lastName": lastName,
    "email": email,
    "mobile": mobile,
  };
}

传递参数时按如下方式处理：

// 1. 构造员工对象列表
List<NewEmployeeInput> newEmployees = [
  NewEmployeeInput(firstName: "张", lastName: "三", email: "zhangsan@example.com", mobile: "13xxxxxxxxx"),
  NewEmployeeInput(firstName: "李", lastName: "四", email: "lisi@example.com", mobile: "13xxxxxxxxx"),
];

// 2. 转成纯Map数组，直接传给variables的employees字段
final variables = {
  "storeId": "你的门店ID",
  "merchantId": "你的商户ID",
  "employees": newEmployees.map((e) => e.toJson()).toList(),
};

第三步：发起请求的正确示例（以graphql_flutter包为例） #

final QueryOptions options = QueryOptions(
  document: gql(inviteEmployeeMutation),
  variables: variables,
);

final result = await client.mutate(options);

// 处理返回结果
if (result.hasException) {
  print(result.exception.toString());
} else {
  final employees = result.data?['invitationEmployee']['nodes'];
  // 后续业务逻辑
}

内容的提问来源于stack exchange，提问作者Basel Abuhadrous