找不到字段的设置器-将Kotlin与Room数据库一起使用 [英] Cannot find setter for field - using Kotlin with Room database

问题描述

我正在与Room持久性库集成.我在Kotlin中有一个数据类，例如:

I'm integrating with the Room persistence library. I have a data class in Kotlin like:

@Entity(tableName = "story")
data class Story (
        @PrimaryKey val id: Long,
        val by: String,
        val descendants: Int,
        val score: Int,
        val time: Long,
        val title: String,
        val type: String,
        val url: String
)

@Entity和@PrimaryKey批注用于Room库.当我尝试构建时，它失败并显示错误:

The @Entity and @PrimaryKey annotations are for the Room library. When I try to build, it is failing with error:

Error:Cannot find setter for field.
Error:Execution failed for task ':app:compileDebugJavaWithJavac'.
> Compilation failed; see the compiler error output for details.

我还尝试提供默认的构造函数:

I also tried providing a default constructor:

@Entity(tableName = "story")
data class Story (
        @PrimaryKey val id: Long,
        val by: String,
        val descendants: Int,
        val score: Int,
        val time: Long,
        val title: String,
        val type: String,
        val url: String
) {
    constructor() : this(0, "", 0, 0, 0, "", "", "")
}

但是这也不起作用.要注意的一点是，如果我将此Kotlin类转换为具有getter和setter的Java类，则它可以工作.感谢您的帮助！

But this doesn't work as well. A thing to note is that it works if I convert this Kotlin class into a Java class with getters and setters. Any help is appreciated!

推荐答案

由于您的字段已标记为val，因此它们实际上是最终字段，并且没有设置器字段.

Since your fields are marked with val, they are effectively final and don't have setter fields.

尝试用var切换val. 您可能还需要初始化字段.

Try switching out the val with var. You might also need to initialize the fields.

@Entity(tableName = "story")
data class Story (
        @PrimaryKey var id: Long? = null,
        var by: String = "",
        var descendants: Int = 0,
        var score: Int = 0,
        var time: Long = 0L,
        var title: String = "",
        var type: String = "",
        var url: String = ""
)

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