Created
September 6, 2024 09:12
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Scala's implicit singleton dependency injection is implemented in the language itself, rather than implicitly in a framework like in Java, or done explicitly.
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| // Define a trait for a generic Database Access Object | |
| trait UserDao { | |
| def getUser(id: Int): String | |
| } | |
| // Concrete implementation of UserDao | |
| class UserDaoImpl extends UserDao { | |
| def getUser(id: Int): String = s"User with ID $id" | |
| } | |
| // Implicit instance of UserDao | |
| implicit val userDao: UserDao = new UserDaoImpl() | |
| // Service that requires a UserDao to perform its operations | |
| class UserService(implicit dao: UserDao) { | |
| def getUserInfo(userId: Int): String = { | |
| dao.getUser(userId) | |
| } | |
| } | |
| @main def main(): Unit = { | |
| val userService = new UserService() | |
| // Usage of the service without explicitly passing the UserDao | |
| val userInfo = userService.getUserInfo(5) // Implicitly uses the userDao | |
| println(userInfo) // Outputs: "User with ID 5" | |
| } |
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