GraphQL-返回取决于参数的计算类型 [英] GraphQL - return calculated type dependent on argument

问题描述

概述(简体):

在NodeJS服务器中，我实现了以下GraphQL模式:

In my NodeJS server I've implemented the following GraphQL schema:

type Item {
  name: String,
  value: Float
}


type Query {
  items(names: [String]!): [Item]
}

然后，客户端查询传递一个名称数组作为参数:

The client query then passes an array of names, as an argument:

{
  items(names: ["total","active"] ) {
    name
    value
  }
}

后端API向mysql数据库查询"总计"和"活动"字段(我的数据库表中的列)，并减少响应，如下所示:

The backend API queries a mysql DB, for the "total" and "active" fields (columns on my DB table) and reduces the response like so:

[{"name":"total" , value:100} , {"name":"active" , value:50}]

---

我希望我的graphQL API支持比率"项，即:我想发送以下查询:

---

I would like my graphQL API to support "ratio" Item, I.E: I would like to send the following query:

{
  items(names: ["ratio"] ) {
    name
    value
  }
}

或

{
  items(names: ["total","active","ratio"] ) {
    name
    value
  }
}

并返回 active/total 作为该新字段([{"name":"ratio" , value:0.5}])的计算结果.以不同的方式处理"比率"字段的通用方法是什么?

And return active / total as the calculated result of that new field ([{"name":"ratio" , value:0.5}]). What would be a generic way to handle the "ratio" field differently?

应该是我的架构中的新类型，还是应该在化简器中实现逻辑?

Should it be a new type in my schema or should I implement the logic in the reducer?

推荐答案

Joe的答案(一旦从数据库中获取结果后，将{"name":"ratio" , value:data.active/data.total}追加到结果中)将无需进行任何模式更改.

Joe's answer (append {"name":"ratio" , value:data.active/data.total} to the result once the result is fetched from database) would do it without making any schema changes.

作为替代方法或在GraphQL中更优雅的方法，可以在类型本身中指定字段名称，而不用将其作为参数传递.然后通过编写解析器来计算ratio.

As an alternative method or as a more elegant way to do it in GraphQL, the field names can be specified in the type itself instead of passing them as arguments. And compute ratio by writing a resolver.

因此，GraphQL模式将是:

So, the GraphQL schema would be:

Item {
  total: Int,
  active: Int,
  ratio: Float
}

type Query {
  items: [Item]
}

客户端指定字段:

{
  items {
    total 
    active 
    ratio
  }
}

ratio可以在解析器内部计算.

And ratio can be calculated inside the resolver.

这是代码:

const express = require('express');
const graphqlHTTP = require('express-graphql');
const { graphql } = require('graphql');
const { makeExecutableSchema } = require('graphql-tools');
const getFieldNames = require('graphql-list-fields');

const typeDefs = `
type Item {
  total: Int,
  active: Int,
  ratio: Float
}

type Query {
  items: [Item]
}
`;

const resolvers = {
  Query: {
    items(obj, args, context, info) {
      const fields = getFieldNames(info) // get the array of field names specified by the client
      return context.db.getItems(fields)
    }
  },
  Item: {
    ratio: (obj) => obj.active / obj.total // resolver for finding ratio
  }
};

const schema = makeExecutableSchema({ typeDefs, resolvers });

const db = {
  getItems: (fields) => // table.select(fields)
    [{total: 10, active: 5},{total: 5, active: 5},{total: 15, active: 5}] // dummy data
}
graphql(
  schema, 
  `query{
    items{
      total,
      active,
      ratio
    }
  }`, 
  {}, // rootValue
  { db } // context
).then(data => console.log(JSON.stringify(data)))

这篇关于GraphQL-返回取决于参数的计算类型的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！