出现错误:(55, 41) Kotlin:类型推断失败
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【中文标题】出现错误:(55, 41) Kotlin:类型推断失败【英文标题】:Getting Error:(55, 41) Kotlin: Type inference failed 【发布时间】:2019-09-05 08:49:06 【问题描述】:我收到Error:(55, 41) Kotlin: Type inference failed. Expected type mismatch: inferred type is (Mutable)List<Optional<Address!>!>! but List<Address>? was expected
我将数据保存到我的 build.gradle 的 mongoDB 文档中:
implementation 'org.springframework.boot:spring-boot-starter-actuator'
implementation 'org.springframework.boot:spring-boot-starter-data-mongodb'
implementation 'org.springframework.boot:spring-boot-starter-data-rest'
implementation 'org.springframework.boot:spring-boot-starter-hateoas'
implementation 'org.springframework.boot:spring-boot-starter-web'
implementation 'com.fasterxml.jackson.module:jackson-module-kotlin'
我的文档对象
@Document(collection = "address")
class Address
@Id
var id: String? = null
var number: String? = null
var street: String? = null
var neighborhood: String? = null
var locality: String? = null
var region: String? = null
var country: String? = null
var code: String? = null
var google_place_id: String? = null
constructor()
和
@Document(collection = "person")
class Person
@Id
var id: String? = null
var name: String? = null
var lastName: String? = null
var phone: String? = null
var email: String? = null
var password: String? = null
@DBRef(db = "mlm")
var address: List<Address>? = null
constructor()
我有接口
@Repository
interface PersonRepository : MongoRepository<Person, String>
和
@Repository
interface AddressRepository : MongoRepository<Address, String>
我的控制器工作 我的播种机/井测试真的要看看如何做到这一点,这就是我遇到问题的地方
class DbSeeder
@Autowired
private val personRepository: PersonRepository? = null
@Autowired
private val addressRepository: AddressRepository? = null
fun addressLoading()
val address1 = Address()
address1.id = "5cb2e9424274072ec4bb4199"
address1.number = "1"
address1.street = "Microsoft Way"
address1.neighborhood = "Redmond"
address1.locality = "King County"
address1.region = "Washington"
address1.code = "425"
address1.country = "United States"
address1.google_place_id = "5644+83 Centurion"
val address2 = Address()
address2.id = "5cb2e9424274072ec4bb4198"
address2.number = "1600"
address2.street = "Amphitheatre Parkway"
address2.neighborhood = ""
address2.locality = "Mountain View"
address2.region = "California"
address2.country = "United States"
address2.code = "94043"
address2.google_place_id = "CWC8+Q9 Mountain View, California, USA"
val address = Arrays.asList(address1, address2)
this.addressRepository!!.insert(address)
fun personLoading()
val personDocument = Person()
personDocument.id = "5cb2e9424274072ec4bb4197"
personDocument.name = "William"
personDocument.lastName = "Gates"
personDocument.phone = "1081010810"
personDocument.email = "bill.gates@gmail.com"
personDocument.password = "bill-secret"
val personAddressDBRef = addressRepository!!.findById("5cb2e9424274072ec4bb4199")
personDocument.address = Arrays.asList(personAddressDBRef)
// val personDBRef = personRepository!!.save(personDocument) // If the ObjectID is requires else ware
personRepository!!.save(personDocument)
要保存我的地址,我需要找到与 ObjectID 相关的地址,然后将 ObjectID 保存为个人文档中的 DBRef
val personAddressDBRef = addressRepository!!.findById("5cb2e9424274072ec4bb4199")
personDocument.address = Arrays.asList(personAddressDBRef) // << Error here
在最后一行我收到错误Error:(55, 41) Kotlin: Type inference failed. Expected type mismatch: inferred type is (Mutable)List<Optional<Address!>!>! but List<Address>? was expected
我似乎不知道如何继续
我在 GitHub 上提供了它https://github.com/Morons/gofetchbyidandinsertdbref.git
任何帮助将不胜感激
【问题讨论】:
这里显示的错误来自日志,没有错误@yole你有解决方案吗? 错误没有正确显示错误。因为它们包含<
和>
,所以它们需要用反引号转义。
【参考方案1】:
您需要阅读https://kotlinlang.org/docs/reference/java-interop.html#null-safety-and-platform-types 以了解推断类型的编写方式。但问题很简单:
personAddressDBRef
具有 Optional<Address>
类型,因为这是 findById
返回的内容。
所以Arrays.asList(personAddressDBRef)
是List<Optional<Address>>
(同样,请参阅上面的链接了解为什么您会看到更复杂的类型)。
您不能将personDocument.address
设置为List<Optional<Address>>
,而是需要List<Address>
。
因此您需要决定如何将Optional<Address>
转换为List<Address>
。一种方法是
personDocument.address = personAddressDBRef.map listOf(it) .orElseGet listOf()
【讨论】:
是什么导致 Bundle parcelables 出现Type inference failed
错误?
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