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配置 Schema
配置 Schema使用"field to input"

使用"field to input"

在同一个 Query 中获取某个字段的值、对其进行处理，并将其作为输入传递给另一个字段。

使用方法

要引用某个字段的值，需使用"Variable"语法 $，并在字段别名或名称前加上 __。（例如，excerpt 字段的值引用为 $__excerpt。）第二个字段的响应本身也可以作为另一个字段的输入：

{
  posts {
    excerpt
 
    # Referencing previous field with name "excerpt"
    isEmptyExcerpt: _isEmpty(value: $__excerpt)
 
    # Referencing previous field with alias "isEmptyExcerpt"
    isNotEmptyExcerpt: _not(value: $__isEmptyExcerpt)
  }
}

响应结果如下：

{
  "data": {
    "posts": [
      {
        "excerpt": "Some post excerpt",
        "isEmptyExcerpt": false,
        "isNotEmptyExcerpt": true
      },
      {
        "excerpt": "",
        "isEmptyExcerpt": true,
        "isNotEmptyExcerpt": false
      }
    ]
  }
}

字段只能被同一节点中位于其之前的兄弟字段引用。以下 Query 将无法正常工作：

# This will fail because the reference to the field must appear after the field, not before
{
  posts {
    isEmptyExcerpt: _isEmpty(value: $__excerpt)
    excerpt
  }
}
 
# This will fail because the reference must be done within the same node
{
  posts {
    excerpt
  }
  isEmptyExcerpt: _isEmpty(value: $__excerpt)
}

字段也不能从指令参数中引用（如需此功能，请使用 @passOnwards 指令）：

# This will fail because the reference can be only used as input to a field, not to a directive
{
  posts {
    hasComments
    title @include(if: $__hasComments)
  }
}

示例

如果文章摘要为空，则改用标题：

{
  posts {
    title
    originalExcerpt: excerpt
    isEmptyExcerpt: _isEmpty(value: $__originalExcerpt)
    excerpt: if(condition: $__isEmptyExcerpt, then: $__title, else: $__originalExcerpt)
  }
}

从外部 REST 端点获取数据，并根据需求对数据进行处理。

{
  externalData: _getJSON(url: "https://example.com/rest/some-external-endpoint")
  userName: _extract(object: $__externalData, path: "data.user.name")
  userLastName: _extract(object: $__externalData, path: "data.user.surname")
}

这将产生以下结果：

{
  "data": {
    "externalData": {
      "data": {
        "user": {
          "id": 1,
          "name": "Leo",
          "surname": "Loso"
        }
      }
    },
    "userName": "Leo",
    "userLastName": "Loso"
  }
}

对 externalData 使用 @remove 指令，还可以避免在响应中输出外部端点的原始数据：

{
  externalData: _getJSON(url: "https://example.com/rest/some-external-endpoint") @remove
  userName: _extract(object: $__externalData, path: "data.user.name")
  userLastName: _extract(object: $__externalData, path: "data.user.surname")
}

这将产生以下结果：

{
  "data": {
    "userName": "Leo",
    "userLastName": "Loso"
  }
}

获取每位用户中提及该用户邮箱的文章：

{
  users {
    email
    posts(filter: { search: $__email }) {
      id
      title
    }
  }
}

通过 optionValue 字段定义 to 和 from 邮箱地址，并发送新闻通讯：

mutation {
  fromEmail: optionValue(name: "admin_email")
  toEmail: optionValue(name: "subscribers_email_list_recipient_address")
  _sendEmail(
    from: {
      email: $__fromEmail
    }
    to: $__toEmail
    subject: "Weekly summary"
    messageAs: {
      html: "..."
    }
  )
}