Javascript 使用GraphQL在单个字段上设置解析器

我想在返回字符串的单个字段上设置一个解析器

对于这个例子。我想获取title属性，并使其成为.toUpperCase

模式 分解器 以下是解决方案：

const resolvers = {
  Product: {
    title: product => {
      return product.title.toUpperCase();
    }
  },
  Query: {
    products: () => [{title:'foo'}]
  }
};

typeDefs：

type Product {
  title: String!
}
type Query {
  products: [Product]
}

另一种方法是使用自定义指令，如@upperCase，但它太复杂了

更新指令方式

@大写指令实现：

import { SchemaDirectiveVisitor } from 'graphql-tools';
import { GraphQLField, defaultFieldResolver } from 'graphql';

class UppercaseDirective extends SchemaDirectiveVisitor {
  public visitFieldDefinition(field: GraphQLField<any, any>) {
    const { resolve = defaultFieldResolver } = field;
    field.resolve = async function resolver(...args) {
      const result = resolve.apply(this, args);
      if (typeof result === 'string') {
        return result.toUpperCase();
      }
      return result;
    };
  }
}

export { UppercaseDirective };

模式：

---

以下是源代码：

谢谢，但这似乎不对。每次都可以使用title.toUpperCase。我想给它传递一个参数，以确定它是否应该。啊，我看到了棘手的部分——将其称为模式类型本身。奇怪的是，我可以为产品命名任何我想要的东西——但不能查询。我现在明白了。Thanks@Ycon更新graphql指令方式谢谢-对于这样的用例，指令方式似乎有点冗长，但很好知道

type Product {
  title: String!
}
type Query {
  products: [Product]
}

import { SchemaDirectiveVisitor } from 'graphql-tools';
import { GraphQLField, defaultFieldResolver } from 'graphql';

class UppercaseDirective extends SchemaDirectiveVisitor {
  public visitFieldDefinition(field: GraphQLField<any, any>) {
    const { resolve = defaultFieldResolver } = field;
    field.resolve = async function resolver(...args) {
      const result = resolve.apply(this, args);
      if (typeof result === 'string') {
        return result.toUpperCase();
      }
      return result;
    };
  }
}

export { UppercaseDirective };

const typeDefs: string = `
  enum Status {
    SOLD_OUT
    NO_STOCK
    OUT_OF_DATE @deprecated(reason: "This value is deprecated")
  }

  type Book {
    id: ID!
    title: String @uppercase
    author: String
    status: Status
    name: String @deprecated(reason: "Use title instead")
  }

  type Query {
    books: [Book]!
    bookByStatus(status: Status!): [Book]!
  }
`;

const schema: GraphQLSchema = makeExecutableSchema({
  typeDefs,
  resolvers,
  schemaDirectives: {
    deprecated: DeprecatedDirective,
    uppercase: UppercaseDirective
  }
});