CODEWITHSUNDEEP
javaandroidmvvmviewmodeldao
Senthamizh
Senthamizh

Reputation: 113

Android mvvm architecture trouble understanding process flow

I am learning about implementing MVVM architecture in android and I have trouble understanding the process flow. I cannot understand how the dao class is connected to the database class and how the POJO from the model class is added to the database.

Here is what I have I understood.

  1. Model class: It is a POJO class which holds the folder structure.

  2. Dao It holds all the CRUD operations that needs to be performed on the db with a method attached to them through which they can be called.

  3. Database class It extends RoomDatabase and creates and returns a db instance. It also holds an abstract method which returns the Dao.

Here is my code (I actually have more, but I have provided only the area I lack understanding):

  1. Model class

` @Entity

public class InventoryModel {

@PrimaryKey (autoGenerate = true)
public int id;
private String itemName;
private int itemQuantity;
private double itemPrice;

public InventoryModel(String itemName, int itemQuantity, double itemPrice){
    this.itemName = itemName;
    this.itemQuantity = itemQuantity;
    this.itemPrice = itemPrice;
}

2.Dao

@Dao
public interface InventoryModelDao {

@Query("SELECT * FROM InventoryModel")
LiveData<List<InventoryModel>> getAllInventoryItems();

@Insert(onConflict = OnConflictStrategy.ABORT)
void addItem(InventoryModel inventoryModel);

 @Delete
void deleteItem(InventoryModel inventoryModel);
}

3.Database class (I have only included the abstract method. the excluded part returns an instance of db)

public abstract InventoryModelDao inventoryModelDao();

How exactly does the Dao connect to the database?

Upvotes: 0

Views: 75

Answers (2)

Crompy
Crompy

Reputation: 745

To extend a_local_nobody's answer. You can find the generated classes under app\build\generated\source\apt\debug\PACKAGE\dao\InventoryModelDao_Impl

Upvotes: 1

a_local_nobody
a_local_nobody

Reputation: 8191

The Data access object generates a lot of boilerplate code for us underneath when we specify things such as @Delete, @Insert and @Query operations and you won't ever see this generated code, but internally these methods are converted to methods which execute on the database itself.

The Dao is therefore the operations which execute on your database through generated code internally

Upvotes: 2

Related Questions