Add solution for gorm challenge-1-crud-operations by shansing (#1458)

* Add solution for gorm challenge-1-crud-operations

* fix: transaction for user update and deletion

---------

Co-authored-by: go-interview-practice-bot[bot] <230190823+go-interview-practice-bot[bot]@users.noreply.github.com>

Author: shansing

packages/gorm/challenge-1-crud-operations/submissions/shansing/solution.go

@@ -0,0 +1,105 @@
+package main
+
+import (
+	"errors"
+	"fmt"
+	"time"
+
+	"gorm.io/driver/sqlite"
+	"gorm.io/gorm"
+)
+
+// User represents a user in the system
+type User struct {
+	ID        uint   `gorm:"primaryKey"`
+	Name      string `gorm:"not null"`
+	Email     string `gorm:"unique;not null"`
+	Age       int    `gorm:"check:age > 0"`
+	CreatedAt time.Time
+	UpdatedAt time.Time
+}
+
+// ConnectDB establishes a connection to the SQLite database
+func ConnectDB() (*gorm.DB, error) {
+	// Implement database connection
+	db, err := gorm.Open(sqlite.Open("test.db"), &gorm.Config{})
+	if err != nil {
+		return nil, err
+	}
+	err = db.AutoMigrate(&User{})
+	if err != nil {
+		return nil, err
+	}
+	return db, nil
+}
+
+// CreateUser creates a new user in the database
+func CreateUser(db *gorm.DB, user *User) error {
+	// Implement user creation
+	result := db.Create(user)
+	if result.Error != nil {
+		return result.Error
+	}
+	return nil
+}
+
+// GetUserByID retrieves a user by their ID
+func GetUserByID(db *gorm.DB, id uint) (*User, error) {
+	// Implement user retrieval by ID
+	var user User
+	result := db.First(&user, id)
+	if result.Error != nil {
+		return nil, result.Error
+	}
+	return &user, nil
+}
+
+// GetAllUsers retrieves all users from the database
+func GetAllUsers(db *gorm.DB) ([]User, error) {
+	// Implement retrieval of all users
+	var users []User
+	result := db.Find(&users)
+	if result.Error != nil {
+		return nil, result.Error
+	}
+	return users, nil
+}
+
+// UpdateUser updates an existing user's information
+func UpdateUser(db *gorm.DB, user *User) error {
+	// Implement user update
+	return db.Transaction(func(tx *gorm.DB) error {
+		if u := tx.First(&User{}, user.ID); u.Error != nil {
+			if errors.Is(u.Error, gorm.ErrRecordNotFound) {
+				return fmt.Errorf("user with id %d not found", user.ID)
+			}
+			return fmt.Errorf("user with id %d error", user.ID)
+		}
+		result := tx.Save(user)
+		if result.Error != nil {
+			return result.Error
+		}
+		return nil
+	})
+}
+
+// DeleteUser removes a user from the database
+func DeleteUser(db *gorm.DB, id uint) error {
+	// Implement user deletion
+	return db.Transaction(func(tx *gorm.DB) error {
+		if u := tx.First(&User{}, id); u.Error != nil {
+			if errors.Is(u.Error, gorm.ErrRecordNotFound) {
+				return fmt.Errorf("user with id %d not found", id)
+			}
+			return fmt.Errorf("user with id %d error", id)
+		}
+		result := tx.Delete(&User{}, id)
+		if result.Error != nil {
+			return result.Error
+		}
+		if result.RowsAffected == 0 {
+			return fmt.Errorf("user with id %d not found", id)
+		}
+		return nil
+	})
+}