How kotlin captures variables and constants in context

Lambda expressions or anonymous functions can access or modify variables and constants in their context. This process is called capture.

fun main(args: Array<String>) {
 //定义一个函数，该函数的返回值类型为()->List<String>
 fun makeList(ele: String): () -> List<String> {
  //创建一个不包含任何元素的List
  var list: MutableList<String> = mutableListOf()
  fun addElement(): List<String> {
   //向list集合中添加一个元素
   list.add(ele)
   return list
  }
  return ::addElement
 }
}

In the above example, a local function can access or modify the variables in its function.

Lambda expressions or anonymous functions will hold a copy of the variables they capture, so on the surface, addelement() accesses the list collection variables of makelist() function, but as long as the program returns a new addelement() function, addelement() function will hold a new copy of list.

Lambda expressions or anonymous functions will hold a copy of the variables they capture. Therefore, on the surface, addelement() accesses the list collection variables of makelist() function. As long as the program returns a new addelement() function, it will hold a new copy of list.

fun main(args: Array<String>) {
 println("******add1返回的List**********")
 val add1 = makeList("刘备")
 println(add1())
 println(add1())

 println("******add2返回的List**********")
 val add2 = makeList("关羽")
 println(add2())
 println(add2())
}

Output results:

summary

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