如何在聚合管道中将bool转换为字符串并更改其值

Question

具有带有记录的集合，需要将列的布尔值转换为字符串：

[
  {
    _id: "bmasndvhjbcw",
    name: "lucas",
    occupation: "scientist",
    passed_phd: true,
    age: 55,
    location: "texas",

  },
  {
    _id: "bmasndvhjbcx",
    name: "mark",
    occupation: "scientist",
    age: 45,
    passed_phd: true,
    location: "texas",

  },
  {
    _id: "bmasndvhjbca",
    name: "stuart",
    occupation: "lab assistant",
    age: 25,
    passed_phd: false,
    location: "texas",

  },
  {
    _id: "bmasndvhjbcq",
    name: "cooper",
    occupation: "physicist",
    age: 69,
    passed_phd: false,
    location: "texas"
  }
]

如何将记录的布尔值更改为字符串。

passed_phd中具有true（boolean）的值应转换为“ yes”（string）

passed_phd中具有false（boolean）的值应转换为“ no”（string）

[
  {
    _id: "bmasndvhjbcw",
    name: "lucas",
    occupation: "scientist",
    passed_phd: "yes",
    age: 55,
    location: "texas",

  },
  {
    _id: "bmasndvhjbcx",
    name: "mark",
    occupation: "scientist",
    age: 45,
    passed_phd: "yes",
    location: "texas",

  },
  {
    _id: "bmasndvhjbca",
    name: "stuart",
    occupation: "lab assistant",
    age: 25,
    passed_phd: "no",
    location: "texas",

  },
  {
    _id: "bmasndvhjbcq",
    name: "cooper",
    occupation: "physicist",
    age: 69,
    passed_phd: "no",
    location: "texas"
  }
]

mongodb 4.0版

尝试过此：

{passed_phd : [{'passed_phd':true},{$set:{'passed_phd':"yes"}] }

错误：预期为“ [”或AggregationStage，但找到“ {”。

Answer 1

您需要使用$toString，请尝试在以下阶段添加：

{
    $addFields: {
      passed_phd: {
        $toString: "$passed_phd"
      }
    }
  }

测试： MongoDB-Playground