Saving Data on Android

@Embedded
The 
@Embedded
 annotation can be used on an entity's field to tell Room that the 
properties on the annotated object should be represented as columns on the same 
entity.
For example, say that you have a 
User
 table that contains address information. Your 
entity could look like this:
@Entity
 
data
 
class
 
User
( 
    
@PrimaryKey
 
val
 id: 
Int
,
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Chapter 6: Entity Definitions
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110

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val
 firstName: String?, 
    
val
 street: String?, 
    
val
 state: String?, 
    
val
 city: String?, 
    
@ColumnInfo(name = "post_code")
 
val
 postCode: 
Int
 
)
However, thanks to the 
@Embedded
 annotation you can represent the address fields 
as a separate class but Room will still generate a single table:
data
 
class
 
Address
( 
    
val
 street: String?, 
    
val
 state: String?, 
    
val
 city: String?, 
    
@ColumnInfo(name = "post_code")
 
val
 postCode: 
Int
 
) 
 
@Entity
 
data
 
class
 
User
( 
    
@PrimaryKey
 
val
 id: 
Int
, 
    
val
 firstName: String?, 
    
@Embedded
 
val
 address: Address? 
)
Both implementations will generate a single 
User
 table with six fields: 
id
, 
firstName
, 
street
, 
state
, 
city
 and 
postCode
.
There are more annotations available, but these are by far the most commonly used 
when creating your entities.
Now that you know the theory, it is time to put it into practice!
Crea/ng your en//es
Since you'll be working on with Room, make sure you've opened the 
starter
 project, 
located in the 
entity-definitions 
▸
 projects
 folder.
Now, once Android studio finishes indexing the code, you need to add the 
appropriate dependencies to your 
build.gradle
 files to use Room. To ensure forward 
compatibility with future versions of Android, you will use 
Androidx
 artifacts for 
this project.
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Open the app-level 
build.gradle
 file and add the following lines under the 
dependencies block:
//Room
 
implementation 
"androidx.room:room-common:$room_version"
 
kapt 
"androidx.room:room-compiler:$room_version"
 
implementation 
"androidx.room:room-runtime:$room_version"
Press 
Sync Now
 and wait until Android Studio finishes syncing your new 
dependencies.
Build and run your app one more time just to make sure that the project is still 
working properly after the updates to your gradle files.
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Chapter 6: Entity Definitions
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Create a new package under the root directory of your app by right-clicking on