scala

问题 I need to apply a filter on an attribute of an optional table produced by a left join in scala slick . I could not find any documentation on this or any similar questions online. Consider the following query: val query = FirstTable joinLeft SecondTable on (_.foreignId === _.id) I would like to filter is by an attribute of the SecondTable : query.filter { case (firstTable, secondTableOpt) => secondTableOpt.attribute === "value" } Obviously this does not compile since secondTableOpt is a Rep

问题 I need to apply a filter on an attribute of an optional table produced by a left join in scala slick . I could not find any documentation on this or any similar questions online. Consider the following query: val query = FirstTable joinLeft SecondTable on (_.foreignId === _.id) I would like to filter is by an attribute of the SecondTable : query.filter { case (firstTable, secondTableOpt) => secondTableOpt.attribute === "value" } Obviously this does not compile since secondTableOpt is a Rep

问题 I'm trying to write a function which takes an Int and returns all of the prime numbers up to and including that Int. for example "list of primes for 8" = List(3,5,7) This is what I have so far : def isPrime(i: Int): Boolean = { if (i <= 1) false else if (i == 2) true else !(2 to (i - 1)).exists(x => i % x == 0) } //> isPrime: (i: Int)Boolean def getListOfPrimesToN(n : Int) = { } for the function getListOfPrimesToN I plan to 1. create a List "l" of size n and populate it with elements ranging

问题 I need to upload a local file to Google Cloud Storage using Scala language. What is the easiest way to do it? This file will also need to be public downloaded later. 回答1: Use the java library provided by Google. It will work with scala as well. They provide an example of how to use this library here. It's in java but the scala equivalent should be easy to code. 来源： https://stackoverflow.com/questions/25540158/how-to-easily-send-local-file-to-google-cloud-storage-in-scala

问题 I need to upload a local file to Google Cloud Storage using Scala language. What is the easiest way to do it? This file will also need to be public downloaded later. 回答1: Use the java library provided by Google. It will work with scala as well. They provide an example of how to use this library here. It's in java but the scala equivalent should be easy to code. 来源： https://stackoverflow.com/questions/25540158/how-to-easily-send-local-file-to-google-cloud-storage-in-scala

问题 Based on a previous question, the following code compiles OK trait Logger { def log(msg: String): Unit } trait LoggerA extends Logger { def log(msg: String) = ??? } trait LoggerB extends Logger { override def log(msg: String) = ??? } class Logged1 extends LoggerA class Logged2 extends LoggerB class Logged3 extends LoggerA with LoggerB The override is not required in LoggerA because there is no concrete implementation of log in Logger . However if I remove the override from LoggerB it no

问题 Based on a previous question, the following code compiles OK trait Logger { def log(msg: String): Unit } trait LoggerA extends Logger { def log(msg: String) = ??? } trait LoggerB extends Logger { override def log(msg: String) = ??? } class Logged1 extends LoggerA class Logged2 extends LoggerB class Logged3 extends LoggerA with LoggerB The override is not required in LoggerA because there is no concrete implementation of log in Logger . However if I remove the override from LoggerB it no

问题 My application code uses AService trait AService { def registerNewUser (username: String)(implicit tenant: Tenant): Future[Response] } to register a new user. Class Tenant is a simple case class: case class Tenant(val vstNumber:String, val divisionNumber:String) Trait AServiceMock mimics the registration logic by using a mocked version of AService trait AServiceMock { def registrationService = { val service = mock[AService] service.registerNewUser(anyString) returns Future(fixedResponse)

问题 My application code uses AService trait AService { def registerNewUser (username: String)(implicit tenant: Tenant): Future[Response] } to register a new user. Class Tenant is a simple case class: case class Tenant(val vstNumber:String, val divisionNumber:String) Trait AServiceMock mimics the registration logic by using a mocked version of AService trait AServiceMock { def registrationService = { val service = mock[AService] service.registerNewUser(anyString) returns Future(fixedResponse)

问题 After seeing the method signature of map in scala as def map[A, B](l: List[A])(f: A => B): List[B] = ??? my layman undersanting of [A, B] in above is that they signal the method that we'll be exclusively working with generic Type A and B in the defined method. Now I go on to implement a method to add values from two lists consquetively (basically zipWith) using similar coding pattern. def addCorresponding[Int](l1: List[Int], l2: List[Int]): List[Int] = (l1, l2) match { case (_, Nil) => Nil