房间数据库中的硬编码布尔查询 [英] Hardcode Boolean Query In Room Database

问题描述

我正在构建一个Android应用程序，该应用程序显示用户的潜在匹配项列表.用户可以单击一个来喜欢该用户，而我会将所有这些喜欢保存在本地.

I'm building an Android application that displays a list of potential matches for a user. The user can click on one to like the user, and I save all of those likes locally.

我可以编写查询以获取匹配项列表，如下所示:

I can write a query to get the list of matches like this:

@Query("SELECT * FROM match WHERE liked = :liked ORDER BY match DESC LIMIT :limit")
fun getMatches(limit: Int = 6, liked: Boolean = true): Flowable<List<Match>>

我了解到这很好用.但是，我没有预见到将liked设置为false的任何情况，因此我很好奇是否有一种方法可以对我的布尔条件进行硬编码?如果我尝试:

I've learned that this works fine. However, I don't foresee any scenario where I'll ever set liked to false, and so I'm curious if there is a way to hardcode my Boolean condition? If I try:

@Query("SELECT * FROM match WHERE liked = true ORDER BY match DESC LIMIT :limit")

在编译时出现以下错误:

I get the following error at compile time:

Error:(8, 0) Gradle: error: There is a problem with the query: [SQLITE_ERROR] SQL error or missing database (no such column: true)

如何在查询字符串中硬编码此布尔值?

How can I hard code this Boolean in my query string?

我也尝试过:

• 用单引号引起来的条件
  • @Query("SELECT * FROM match WHERE liked = 'true' ORDER BY match DESC LIMIT :limit")
  • Wrapping the condition in single quotes
    • @Query("SELECT * FROM match WHERE liked = 'true' ORDER BY match DESC LIMIT :limit")

    推荐答案

    SQLite没有布尔数据类型. Room将其映射到INTEGER列，将true映射到1，将false映射到0.

    SQLite does not have a boolean data type. Room maps it to an INTEGER column, mapping true to 1 and false to 0.

    所以，我希望它能起作用:

    So, I would expect this to work:

    @Query("SELECT * FROM match WHERE liked = 1 ORDER BY match DESC LIMIT :limit")
    

    请记住，这种行为是无证的.但是，它不应更改—至少并非没有响亮的响尾蛇响起—因为我们需要使用迁移来处理所有更改.

    Bear in mind that this behavior is undocumented. However, it shouldn't change — at least not without alarm klaxons sounding — as we'd need to use migrations to deal with any changes.

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