Question

const { GraphQLServer } = require('graphql-yoga');
const mongoose = require('mongoose');

mongoose.connect("mongodb://localhost/test1");

const Todo = mongoose.model('Todo',{
    text: String,
    complete: Boolean
});


const typeDefs = `
  type Query {
    hello(name: String): String!
  }
  type Todo{
      id: ID!
      text: String!
      complete: Boolean!
  }
  type Mutation{
      createTodo(text:String!): Todo
  }
`

const resolvers = {
  Query: {
    hello: (_, { name }) => `Hello ${name || 'World'}`,
  },
  Mutation:{
      createTodo: async (_,{ text }) => {
          const todo = new Todo({text, complete: false});
          await todo.save();
          return todo;
      }
  }
};

const server = new GraphQLServer({ typeDefs, resolvers })

mongoose.connection.once("open", function() {
    server.start(() => console.log('Server is running on localhost:4000'))
  });

您好我是节点js和mongoDB的新手。我试图启动我的服务器，但它没有启动。每次出现这样的错误时：

(node:17896) UnhandledPromiseRejectionWarning: Unhandled promise rejection. 
This error originated either by throwing
inside of an async function without a catch block, or by rejecting a promise 
which was not handled with .catch(). (rejection id: 1)
(node:17896) [DEP0018] DeprecationWarning: Unhandled promise rejections are 
deprecated. In the future, promise rejections that are not handled will 
terminate the Node.js process with a non-zero exit code.

每次这都显示出一些承诺错误。任何人都可以帮我调试这个程序。我是初学者。我不太了解它。但根据我的理解，我只编写了正确的代码。

Answer 1

您的保存功能可能会抛出一个您无法处理的箭头！您可以通过以下方式之一解决此问题：

GraphQL自己处理promise，所以这会给你相同的结果：

createTodo: (_,{ text }) => {
      const todo = new Todo({text, complete: false});
      return todo.save();
}

使用try catch可以更好地处理错误：

   createTodo: async (_,{ text }) => {
      const todo = new Todo({text, complete: false});
      try {
           await todo.save();
           return todo;
      } catch(err) {
           \\ do something with error
           console.error('error=>', err);
           return null;
      }
  }

承诺和决心不起作用

1 个答案: