在多种类型上使用GraphQL Fragment

Question

如果我的GraphQL架构中有多个类型共有的字段集,有没有办法做这样的事情？

type Address {
  line1: String
  city: String
  state: String 
  zip: String
}

fragment NameAndAddress on Person, Business {
  name: String
  address: Address
}

type Business {
   ...NameAndAddress
   hours: String
}

type Customer {
   ...NameAndAddress
   customerSince: Date
}

Answer 1

片段仅在发出请求时在客户端使用 - 它们不能在架构中使用.GraphQL不支持类型继承或任何其他机制,可以减少必须为不同类型写出相同字段的冗余.

如果您正在使用apollo-server,构成架构的类型定义只是一个字符串,因此您可以通过模板文字实现您正在寻找的功能:

const nameAndAddress = `
  name: String
  address: Address
`

const typeDefs = `
  type Business {
     ${nameAndAddress}
     hours: String
  }

  type Customer {
     ${nameAndAddress}
     customerSince: Date
  }
`

或者,有些库,如graphql-s2s,允许您使用类型继承.

Answer 2

您可以，但 GraphQL 不会让您在两种类型之间创建片段，除非您在架构中指定这些类型共享相同的属性。为此，您必须使用接口。然后，您将能够在客户端构建此界面的片段。

服务器端架构：

interface NameAndAddress {
  name: String
  address: Address
}


type Address {
  line1: String
  city: String
  state: String 
  zip: String
}

type Business implements NameAndAddress {
  # by design you have to write those properties again
  name: String
  address: Address

  hours: String
}

type Customer implements NameAndAddress {
  name: String
  address: Address

  customerSince: Date
}

然后在你的客户端

# define a fragment on the interface
fragment NameAndAddress on NameAndAddress {
  name: String
  address: Address
}

# you can then get the fields as follow
query {
  business {
     ...NameAndAddress
  }

  customer {
     ...NameAndAddress
  }
}