Annotation 参数必须是编译时常量 [英] An Annotation argument must be a compile time constant

问题描述

我看过这个问题.类似的错误.但在我的情况下是不同的.

i have seen this question. Similar error.But in my case it is different.

在使用 Room 时，我正在创建表格.它工作正常.

While working with Room i was creating table. it was working fine.

@Daointerface 
UserDao {
@Query("SELECT * FROM user")
fun getAll(): List<User>

@Insert(onConflict = OnConflictStrategy.REPLACE)
fun insert(user: User)

@Delete
fun delete(user: User)}

但后来我发现所有表名都必须存储在不同的类中.像表名user"-> 存储在不同的类中.

but then i found all table Names must be stored in a different class. like table name "user" - > Stored in different class.

例如

class Table {
companion object {
    const val USER_TABLE = "user"
}}

但下面的代码不起作用.它没有从 Table 类中获取表名.给出编译时错误.Annotation 参数必须是编译时常量"请帮帮我.它有什么问题

But below code is not working . it is not picking up table name from Table class. Giving compile time error . "An Annotation argument must be a compile time constant" please help me out.What wrong in it

@Query("SELECT * FROM $Table.USER_TABLE")
fun getAll(): List<User>

推荐答案

问题在于错误中所述的问题，您不能为 @Query 注释动态定义参数.如果要在其他地方定义表的名称，请使用字符串连接.你可以这样做:

The problem is the one stated in the error, you can't have dynamically defined arguments for your @Query annotation. If you want to define the name of the table somewhere else, use string concatenation. You can do it like this:

@Query("SELECT * FROM " + Table.USER_TABLE)
fun getAll(): List<User>

这就是他们在这个 google 示例.

This is how they do it in this google sample.

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