graphql-JS Express无法解析字段

Question

当我在节点服务器中执行以下代码时。我看到graphql-JS无法解析字段“product.productTax”的错误。

使用graphql-express，visual studio代码，我试图完全模仿来自http://graphql.org/graphql-js/object-types/的以下代码

<!-- language: lang-js -->
var express = require('express');
var graphqlHTTP = require('express-graphql');
var { buildSchema } = require('graphql');

// Construct a schema, using GraphQL schema language
var schema = buildSchema(`
  type Product{
    product_id: Int!
    sku: String
    short_nm: String
    retl_price: Float!
    productTax(tax_rate: Float!): [Float!]
  }

  type Query {
    getproduct(product_id: Int, sku: String, short_nm: String, retl_price: Float): Product
  }
`);

// This class implements the Product GraphQL type
class Product {

  constructor(product_id, sku, short_nm, retl_price) {
    this.product_id = product_id;
    this.sku = sku;
    this.short_nm = short_nm;
    this.retl_price = retl_price;
  }

  productTax({tax_rate}){
    return this.retl_price * tax_rate / 100;
  }

}

// The root provides the top-level API endpoints
var root = {
  getproduct: function ({product_id, sku, short_nm, retl_price}) {
    return new Product(product_id, sku, short_nm, retl_price);
  }
}

var app = express();
app.use('/graphql', graphqlHTTP({
  schema: schema,
  rootValue: root,
  graphiql: true,
}));
app.listen(4000);
console.log('Running a GraphQL API server at localhost:4000/graphql');

响应

Answer 1

在您的架构中，您有

    productTax(tax_rate: Float!): [Float!]

因此graphql期望一个浮点值数组。它似乎应该是

    productTax(tax_rate: Float!): Float!

因为您的productTax()方法返回一个浮点值。

您还可以添加默认税率。我还没有看到你传递它，所以

    productTax(tax_rate: Float = 20): Float!