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Scala closure

Scala function Scala function

Closure is a function that returns a value dependent on the external declaration in a function or more variables.

Closures Generally considered to be simply another function inside a function can access the local variables.

This anonymous function as the following:

val multiplier = (i:Int) => i * 10  

Function body has a variable i, as a function parameter. Another piece of code like the following:

val multiplier = (i:Int) => i * factor

There are two variables in the multiplier: i and factor. Where i is a formal parameter of the function, the function is called when the multiplier, i was given a new value. However, factor is not the formal parameters, but the free variables, consider the following codes:

var factor = 3  
val multiplier = (i:Int) => i * factor  

Here we introduce a free variable factor, this variable is defined outside of the function.

Multiplier function variables thus defined as a "closure", because it refers to a variable outside the function definition, the definition of the process of this function is to capture the free variables constitute a closed function.

Complete example

object Test {  
   def main(args: Array[String]) {  
      println( "muliplier(1) value = " +  multiplier(1) )  
      println( "muliplier(2) value = " +  multiplier(2) )  
   var factor = 3  
   val multiplier = (i:Int) => i * factor  

Running instance »

Implementation of the above code, the output is:

$ scalac Test.scala  
$  scala Test  
muliplier(1) value = 3  
muliplier(2) value = 6  

Scala function Scala function