使用Room在单个事务中从多个表中获取数据? [英] Fetching data from multiple tables in single transaction using Room?

问题描述

使用房间我正在尝试从两个表(公司和农场)中获取数据到一个列表中.使用通用软件，我创建了一个基类CompanyFarmBase和两个子类Company和Farm.现在使用示例，我使用以下代码创建了Dao类:

Using Room I am trying to fetch data from two tables (Company and Farm) into a single list. Using commonsware answer I created a base class CompanyFarmBase and two child classes Company and Farm. Now using the example I created Dao class with following code:

@Query("SELECT * FROM farm_table")
fun getAllFarm(): List<UserModel.Farm>

@Query("SELECT * FROM company_table")
fun getAllCompany(): List<UserModel.Company>

@Transaction
fun getAllCompanyFarm(): List<UserModel.CompanyFarmBase> {
    val result = ArrayList<UserModel.CompanyFarmBase>()

    result.addAll(getAllCompany())
    result.addAll(getAllFarm())

    return result
}

现在，当我尝试构建时，出现以下错误:

Now when I try to build I get these errors:

dao/FarmDao_Impl.java:100: error: illegal start of expression
  List<UserModel.CompanyFarmBase> _result = FarmDao.DefaultImpls.getAllCompanyFarm(this, );


dagger.internal.codegen.ComponentProcessor was unable to process com.navdeep.di.component.AppComponent because not all of its dependencies could be resolved. Check for compilation errors or a circular dependency with generated code.

请让我知道我哪里出错了.分别查询每个表将提供适当的数据.谢谢！

Please let me know where I went wrong. Querying separately each table gives proper data. Thanks!

推荐答案

最近也有此问题，传入默认参数将解决此问题.为什么，不知道.

Recently had this issue as well, passing in a default parameter will fix the issue. Why, no idea.

@Transaction
fun getAllCompanyFarm(notUsed: Boolean = true): List<UserModel.CompanyFarmBase> {
    val result = ArrayList<UserModel.CompanyFarmBase>()

    result.addAll(getAllCompany())
    result.addAll(getAllFarm())

    return result
}

这篇关于使用Room在单个事务中从多个表中获取数据?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！