Closures {.en}

闭包 {.zh}

::: {.en} Go supports anonymous functions, which can form closures. Anonymous functions are useful when you want to define a function inline without having to name it. :::

::: {.zh}

Go 支持 匿名函数，并能用其构造 闭包。如果要定义一个不需要命名的内联函数，匿名函数非常有用。

:::

  1. package main
  2. import "fmt"

::: {.en} This function intSeq returns another function, which we define anonymously in the body of intSeq. The returned function closes over the variable i to form a closure. :::

::: {.zh}

这个函数 intSeq 返回另一个在 intSeq 的主体内定义的匿名函数。这个返回的函数使用闭包的方式隐藏变量 i。

:::

  1. func intSeq() func() int {
  2.     i := 0
  3.     return func() int {
  4.         i++
  5.         return i
  6.     }
  7. }
  8. func main() {

::: {.en} We call intSeq, assigning the result (a function) to nextInt. This function value captures its own i value, which will be updated each time we call nextInt. :::

::: {.zh}

我们调用 intSeq 函数，将返回值（一个函数）赋给 nextInt。这个函数值包含了自己的 i 值，这样每次调用 nextInt 时都会更新 i 的值。

:::

  1.     nextInt := intSeq()

::: {.en} See the effect of the closure by calling nextInt a few times. :::

::: {.zh}

通过几次调用 nextInt 来查看闭包的效果。

:::

  1.     fmt.Println(nextInt())

::: {.en} To confirm that the state is unique to that particular function, create and test a new one. :::

::: {.zh}

要确认状态对于特定函数是唯一的，我们 重新创建并测试一下。

:::

  1.     newInts := intSeq()
  2.     fmt.Println(newInts())
  3. }
  1. $ go run closures.go
  2. 1
  3. 2
  4. 3
  5. 1

::: {.en} The last feature of functions we’ll look at for now is recursion. :::

::: {.zh}

我们即将要学习的函数的最后一个特性是 递归。

:::