英文:
golang closure(anonymous function)catch wrong parameter`s value
问题
看到你的代码了：
package main
import "fmt"
func main() {
i := 10
closure1 := func() {
fmt.Printf("闭包函数，i的值为：%d\n", i)
i = 15
}
closure1()
fmt.Printf("在main函数中，i的值为：%d\n", i)
closure2 := func(x int) {
fmt.Printf("函数调用，传递参数，i的值为：%d\n", x)
}
i = 20
closure1()
closure2(i)
}
我认为closure2的输出应该是20，但实际结果是15，我不知道为什么？请问有人可以帮助我吗？请查看我在代码中的注释，提前谢谢。
英文:
see test code:
package main
import "fmt"
func main() {
i := 10
closure1 := func() {
fmt.Printf("closure, i: %d\n", i)
i = 15
}
closure1()
fmt.Printf("in main, i: %d\n", i)
closure2 := func(x int) {
fmt.Printf("function call, pass parameter, i: %d\n", x)
}
i = 20
closure1()
closure2(i)
}
I think the output of the closure2 should be 20, but the real result is 15, i do not know why????
anybody can help me , please see my comment in my code, thanks in advance.
答案1
得分: 2
问题在于当你调用closure1()时，你首先将i赋值为15，然后在closure two中打印它。你在将i赋值为20之后才执行closure1()，这就是问题所在。以下是修复你的问题的代码：
package main
import "fmt"
func main() {
i := 10
closure1 := func() {
fmt.Printf("闭包，i：%d\n", i)
i = 15
}
closure1()
fmt.Printf("在main函数中，i：%d\n", i)
closure2 := func(x int) {
fmt.Printf("函数调用，传递参数，i：%d\n", x)
}
closure1()
i = 20 // 现在将其重新赋值为20... 所以下面的结果将变为20...
closure2(i)
}
你看到问题了吗？
英文:
The problem is that your first assigning i to 15 when your calling closure1() And then closure two you print it.. Your doing closure1() after assigning i to 20.. Thats the problem, this should fix your problem:
package main
import "fmt"
func main() {
i := 10
closure1 := func() {
fmt.Printf("closure, i: %d\n", i)
i = 15
}
closure1()
fmt.Printf("in main, i: %d\n", i)
closure2 := func(x int) {
fmt.Printf("function call, pass parameter, i: %d\n", x)
}
closure1()
i = 20 // Now it assigns it back to 20.. So the result below will become 20...
closure2(i)
}
You see your problem?
答案2
得分: 0
closure1的最后一行将i设置为15。这个i属于main()的上下文。
main的倒数第二行再次调用closure1()。所以来自main的i再次被设置为15。
英文:
The last line of closure1 sets i to 15. This i belongs to the main() context.
The next to last line of main calls closure1() again. So the i from main is set to 15 again.
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