#9[30m]. Add IRepo interface.

Author: Evgenii Kanivets

app/src/main/java/com/blogspot/e_kanivets/moneytracker/repo/IRepo.java

@@ -0,0 +1,69 @@
+package com.blogspot.e_kanivets.moneytracker.repo;
+
+import android.database.sqlite.SQLiteOpenHelper;
+import android.support.annotation.NonNull;
+import android.support.annotation.Nullable;
+
+import java.util.List;
+
+/**
+ * Interface that represents a contract of access to abstract storage with CRUD operations.
+ * Created on 2/15/16.
+ *
+ * @author Evgenii Kanivets
+ */
+public interface IRepo<T> {
+    /**
+     * Creates a record with given fields values in storage.
+     *
+     * @param instance is entity instance to be created.
+     * @return created record or null if can't create.
+     */
+    @Nullable
+    T create(T instance);
+
+    /**
+     * Reads a record from storage.
+     *
+     * @param id is identification number of record to be read.
+     * @return read record or null if one not exist.
+     */
+    @Nullable
+    T read(long id);
+
+    /**
+     * Updates a record in storage.
+     *
+     * @param instance is entity instance to be updated.
+     * @return updated record or null if can't update.
+     */
+    @Nullable
+    T update(T instance);
+
+    /**
+     * Deletes a record from storage.
+     *
+     * @param instance is entity instance to be deleted.
+     * @return true if deleted or false if not.
+     */
+    boolean delete(T instance);
+
+    /**
+     * Reads all records from storage.
+     *
+     * @return list of all records. List can't be null, but may be zero sized.
+     */
+    @NonNull
+    List<T> readAll();
+
+    /**
+     * Reads all records from storage that matches given condition. The same as in standard Android
+     * {@link SQLiteOpenHelper}.
+     *
+     * @param condition is a string of selection. For example - "time BETWEEN ? AND ?".
+     * @param args      is a string array with data to be inserted in condition string instead of '?'.
+     * @return list of matched records. List can't be null, but may be zero sized.
+     */
+    @NonNull
+    List<T> readWithCondition(String condition, String[] args);
+}