Room database build errors for @Ignore annotation

Hi,

I’m trying to use Room database within a Kotlin project, but I’m having issues with @Ignore annotation.

I have a data class and I’d like to ignore one field. If I add @Ignore to that field, when I build the project I get several errors saying: “Cannot find setter for field” and one: “Entities and Pojos must have a usable public constructor. You can have an empty constructor or a constructor whose parameters match the fields (by name and type).”

I’ve tried to add a new property within User class from GithubBrowserSample and when I build the project I get the same errors.

[marianperca]

You should move the @Ignore field outside of the constructor, like this:

@Entity(primaryKeys = ["id"])
data class User(
        @field:SerializedName("id")
        val id: Int,

        @field:SerializedName("name")
        val name: String,
    
        @field:SerializedName("age")
        val age: Int
) {
    @Ignore
    val testme: String?
}

[MatthewTighe]

Right, but doesn’t that cause the data class to become mutable? Wouldn’t it need to be var testme: String??

I wanted to retain immutability, so I came up with the following solution:

@Entity(primaryKeys = ["id"])
data class User @Ignore constructor(
    @field:SerializedName("id")
    val id: Int,

    @field:SerializedName("name")
    val name: String,

    @field:SerializedName("age")
    val age: Int,

    @Ignore
    val testme: String?
) {
    constructor(id: Int, name: String, age: Int) : this(id, name, age, null)
}

This allows Room to have only a constructor that matches the fields of the entity.