Recent questions tagged Scala

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scala - How to create an instance of type T at runtime with TypeTags

Here below is how to create a new instance of type T at runtime with Manifest: trait MyTrait class MyClass1(val ... ... Am I missing something? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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735 views

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scala - What does Predef.locally do, and how is it different from Predef.identity

Looking through the Scala 2.8 Predef class, I find that there is a method "locally". As near as I can ... and thus usable anywhere in Scala)? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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836 views

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scala - Should implicit classes always extend AnyVal?

Say I'm writing an extension method implicit class EnhancedFoo(foo: Foo) { def bar() { /* ... */ } } ... make an implicit class a value class? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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693 views

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scala - How to add a new Struct column to a DataFrame

I'm currently trying to extract a database from MongoDB and use Spark to ingest into ElasticSearch with geo_points ... Any help is appreciated! See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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828 views

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scala - How to convert DataFrame to Json?

I have a huge Json file, a small part from it as follows: { "socialNews": [{ "adminTagIds": "", "fileIds": ... or some way to figure it out? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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770 views

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scala - Why is "abstract override" required not "override" alone in subtrait?

I read the section of Programming in Scala where abstract override is introduced, but I'm still confused by ... pertains to stackable traits. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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564 views

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scala - How to set up different databases per environment in Play 2.0?

I'd like my Play app to use different databases for test, local and production (production is Heroku) environments. ... for play test to use? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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631 views

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scala - The cost of nested methods

In Scala one might define methods inside other methods. This limits their scope of use to inside of definition ... answer differ for closures? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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668 views

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scala - Use of option helper in Play Framework 2.0 templates

I'm trying to use views.html.helper.select (documentation here). I don't know scala, so i'm using java. I ... answer didn't helped me a lot. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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566 views

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scala - How to use s3 with Apache spark 2.2 in the Spark shell

I'm trying to load data from an Amazon AWS S3 bucket, while in the Spark shell. I have consulted the following ... to get this working? Thanks. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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805 views

1 answer

scala - Akka SLF4J logback configuration and usage

I have done the following steps to try and configure logging for my akka application: created an application. ... ? Or misconfigured something? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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594 views

1 answer

scala - Integrating native system libraries with SBT

What is a good way to integrate various SBT tasks with native libraries (for example, those from JOGL ... handle native libraries transparently? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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1.4k views

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scala - Slick 3.0 Insert and then get Auto Increment Value

I have written this code which works perfectly class Items(tag: Tag) extends Table[Item](tag, "ITEMS") { ... not answer the question cleanly. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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680 views

1 answer

scala - Idiomatic way to update value in a Map based on previous value

Let's say I store bank accounts information in an immutable Map: val m = Map("Mark" -> 100, "Jonathan" -> ... Is there better way to write this? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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596 views

1 answer

scala - What are views for collections and when would you want to use them?

In Scala, for many (all?) types of collections you can create views. What exactly is a view and for which purposes are views useful? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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719 views

1 answer

scala - How to handle optional query parameters in Play framework

Lets say I have an already functioning Play 2.0 framework based application in Scala that serves a URL such as: ... another way to do this? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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784 views

1 answer

scala - SBT sources in IDEA

I'm using *.scala files in the project folder for configuring my SBT project. I'm using IDEA12 with the Scala Plugin ... I'm using SBT 0.12.3. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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688 views

1 answer

scala - Shapeless - turn a case class into another with fields in different order

I'm thinking of doing something similar to Safely copying fields between case classes of different types but with ... a minimum of boilerplate? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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619 views

1 answer

scala - How to force Logger.debug output in Play! framework specs2 tests?

By default all Logger output, visible when an application is running, is mute when the application is tested. ... shown in the specs2 reports? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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748 views

1 answer

scala - Making stand-alone jar with Simple Build Tool

Is there a way to tell sbt to package all needed libraries (scala-library.jar) into the main package, so it is stand-alone? (static?) See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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2.2k views

1 answer

scala - Iterate rows and columns in Spark dataframe

I have the following Spark dataframe that is created dynamically: val sf1 = StructField("name", StringType, nullable ... each column in Row? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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550 views

1 answer

scala - Get index of current element in a foreach method of Traversable?

Suppose I have two arrays: val ar1 = Array[String]("1", "2", "3") val ar2 = Array[String]("1", ... integer list. Perhaps there is a better way? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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903 views

1 answer

scala - Pattern matching vs if-else

I'm novice in Scala. Recently I was writing a hobby app and caught myself trying to use pattern matching ... than another for some reason? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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877 views

1 answer

scala - Ternary Operator Similar To ?:

I am trying to avoid constructs like this: val result = this.getClass.getSimpleName if (result.endsWith("$")) ... extra stuff to infer types. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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1.0k views

1 answer

scala - SBT to Maven Converter

Since most IDEs are only able to import Maven projects, I'd like to generate a POM.xml from an SBT managed project, ... a better way to do it? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

0 votes

677 views

1 answer

scala - Passing function as block of code between curly braces

A few times I saw a Scala code like that: object Doer{ def doStuff(op: => Unit) { op } } Invoked in ... can use it? Where is it documented? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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662 views

1 answer

scala - What is RDD in spark

Definition says: RDD is immutable distributed collection of objects I don't quite understand what does it mean. Is ... Can some one please help. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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574 views

1 answer

scala - SBT doesn't find file in local maven repository although it's there

I'm having problems with a maven dependency which is in my local respository. SBT can't find it. Already set ... it didn't change anything). See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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