Question

graphql.org/graphql-js上提供的用于创建简单GraphQL实现的Hello World示例如下：

var { graphql, buildSchema } = require('graphql');

// Construct a schema, using GraphQL schema language
var schema = buildSchema(`
    type Query {
        hello: String
    }
`);

// The root provides a resolver function for each API endpoint
var root = {
    hello: () => {
        return 'Hello World!';
    }
};

// Run the GraphQL query '{ hello }' and print out the response
graphql(schema, '{ hello }', root).then((response) => {
    console.log(response);
});

我正在尝试在解析器中运行异步函数，例如数据库调用，而我似乎无法弄清楚如何使其工作：

我正在尝试做什么：

var { graphql, buildSchema } = require('graphql');

// Construct a schema, using GraphQL schema language
var schema = buildSchema(`
    type Query {
        data: String
    }
`);

// The root provides a resolver function for each API endpoint
var root = {
    data: () => {
        getData((data) => {
            return data;    // Returns from callback, instead of from resolver
        }
    }
};

// Run the GraphQL query '{ data }' and print out the response
graphql(schema, '{ data }', root).then((response) => {
    console.log(response);
});

我曾试图使用promises，但似乎没有办法在不进行回调的情况下逃避承诺。我还尝试了各种方法来包装异步getData函数以强制它同步，但最终必须从异步函数返回一个值，同样的问题。我觉得这不是很复杂，我的意思是GraphQL-JS是由Facebook编写的。

Answer 1

所以这个问题在你弄明白之后就变成了你觉得非常愚蠢的问题之一，但是由于我花了多长时间挣扎，我会回答我自己的问题，所以其他人可以从中受益。

事实证明，GraphQL解析器函数必须返回值或解析为该值的promise 。所以我试图用这样的东西做什么：

var { graphql, buildSchema } = require('graphql');

// Construct a schema, using GraphQL schema language
var schema = buildSchema(`
    type Query {
        data: String
    }
`);

// The root provides a resolver function for each API endpoint
var root = {
    data: () => {
        getData((data) => {
            return data;    // Returns from callback, instead of from resolver
        }
    }
};

// Run the GraphQL query '{ data }' and print out the response
graphql(schema, '{ data }', root).then((response) => {
    console.log(response);
});

可以这样做：

var { graphql, buildSchema } = require('graphql');

// Construct a schema, using GraphQL schema language
var schema = buildSchema(`
    type Query {
        data: String
    }
`);

let promiseData = () => {
    return new Promise((resolve, reject) => {
        getData((data) => {
            resolve(data);
        });
    });
};

// The root provides a resolver function for each API endpoint
var root = {
    data: () => {
        return promiseData();
    }
};

// Run the GraphQL query '{ data }' and print out the response
graphql(schema, '{ data }', root).then((response) => {
    console.log(response);
});

如何在需要return语句的GraphQL解析器中调用异步node.js函数？

1 个答案: