android，使用Room和kotlin，如何在字段上添加唯一约束

Question

per Annotate索引和唯一性 ，似乎可以像下面这样添加唯一性约束，

但在AndroidStudio 3中出现错误（编辑器带有红色下划线，表示“ unresolved the reference：indices”），：

/Users/application/database/DbAuthor.kt
Error:(14, 39) Expecting an element

@Entity(tableName = "author" indices = arrayOf(Index(value = "authorid", unique = true)))
class DbAuthor(

    @ColumnInfo(name = "authorid")
    var authorid: Int? = null,

使用Kotlin时如何在字段上添加唯一约束？

gradle就像：

buildscript {
ext {
    verAndroidSupport = '27.0.0'
    arch = "1.0.0"
    archRoomVersion = "1.0.0"

}
ext.kotlin_version = '1.2.20'

和

apply plugin: 'com.android.application'

apply plugin: 'kotlin-android'

apply plugin: 'kotlin-android-extensions'


//arch
implementation "android.arch.lifecycle:runtime:${arch}"
implementation "android.arch.lifecycle:extensions:${arch}"
annotationProcessor "android.arch.lifecycle:compiler:${arch}"
//room
compile "android.arch.persistence.room:runtime:${archRoomVersion}"
annotationProcessor "android.arch.lifecycle:compiler:${arch}"

annotationProcessor "android.arch.persistence.room:compiler:${archRoomVersion}"
kapt "android.arch.persistence.room:compiler:1.0.0-alpha1"

Answer 1

你错过了,后"author"
@Entity(tableName = "author", indices = arrayOf(Index(value = "authorid", unique = true)))