How to use parameter fields in Room @Query?

Question

I have a User class with a field id, so I wanted to run the following query with Room:

@Query("SELECT * FROM ticket where user_id = :user.id")
LiveData<Ticket> loadFromUser(User user);

But I am getting error marks on Android Studio on user.id and all examples I find online only use the direct parameter of the @Query method, usually a String or an int.

Is it possible to use an object's field in a Room @Query? If positive, so what's the proper way of referencing it.

This would be a much needed feature, especially in the case you need to use a high number of members of a class. — AndrewBloom, Feb 10 '20 at 11:24

score 50 · Accepted Answer · answered Aug 15 '18 at 02:14

50

You can't pass parameters like that to room. It does not support a full expression language. You have to use primitive types to pass parameters. Like this,

@Query("SELECT * FROM ticket where user_id = :user_id")
LiveData<Ticket> loadFromUser(String user_id);

answered Aug 15 '18 at 02:14

NirmalCode

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10

So sad that there is no such support :( – Daniel Feb 14 '20 at 14:14
I find room very confining. I find it almost easier to store the Json query and then just parse that later instead of using room. – JPM Oct 19 '21 at 18:20
1

You may add custom method with object parameter as follows: `default LiveData loadFromUser(User user){ return loadFromUser(user.id); }` – Jörg Eisfeld Oct 27 '22 at 23:10
String is not primitive type! – Seyyed Aug 21 '23 at 10:58

score 8 · Answer 2 · answered Dec 07 '20 at 23:47

A simple solution is to create two other functions, one is for user_id and one is for user as follows:

@Query("SELECT * FROM ticket where user_id = :user_id")
LiveData<Ticket> loadFromUser(String user_id);

@Transaction
LiveData<Ticket> loadFromUser(User user){
   return loadFromUser(user.id);
}

score 5 · Answer 3 · answered Dec 15 '19 at 06:38

5

in my case i used @RawQuery

in DAO you can write

@RawQuery
LiveData<Ticket> loadFromUser(SupportSQLiteQuery query);

and create your query and pass to it.

SimpleSQLiteQuery query  = new SimpleSQLiteQuery("SELECT * FROM ticket where user_id = ?") , new Object[]{user.id})

and pass this query to DAO method.

userDao.loadFromUser(query)

answered Dec 15 '19 at 06:38

Mojtaba Haddadi

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That's a lot more complicated for no reason, just use the other solution – Michel Feinstein Dec 15 '19 at 07:19

How to use parameter fields in Room @Query?

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