scala notes - implicit variables

Knowledge point: Implicit variables

important point:

• No declaration, can not be used directly
• A method that cannot find multiple implicit variables at the same time, otherwise an error will be reported
• If a value is explicitly specified, the implicit value has no effect

 

Test code:

 

package demo.scala

object TestImplicit1 {

  def test(implicit name: String) = {
    println("name=" + name)
  }

  def main(args: Array[String]): Unit = {
    //1. Direct call, no implicit parameters, result: name=abc
    test("abc")

    //2.报错：could not find implicit value for parameter name: String
    //test

    //3. Implicit parameters are found and used directly, so test will not report an error, the result: name=implicit_name
    implicit val abc = "implicit_name"
    test

    //4. When the display is specified, the value of the implicit parameter will not be used, the result: name=abc
    test("abc")

    //5. Define another implicit variable of type string, and an error will be reported, because the method test finds two implicit variables of type string: ambiguous implicit values: both value s1 of type String and value abc of type String match expected type String test
    //    implicit val s1 = "s1"
  }
}