英文:
How do I use the strconv.Atoi() method in Go?
问题
我正在尝试在这个小程序中获取用户输入。我尝试了几种方法，使用了strconv.Atoi()方法（我的输入显然是一个字符串，我想将其转换为整数）。这是我的第一次尝试：
package main
import (
"fmt"
"strconv"
)
func main() {
//fmt.Println(strconv.Itoa)
fmt.Println("Say something, in numbers.")
var inputstr string
fmt.Scanln("%s", &inputstr)
input := strconv.Atoi(inputstr)
output := (input * 2)
outputstr := strconv.Itoa(output)
fmt.Println(outputstr)
}
在编译时，我得到了以下错误：
(第19行) strconv.Atoi() 的多值在单值上下文中
然后我查看了Godocs并试图自己解决这个问题，然后意识到还返回了一个错误值。所以，我将
input := strconv.Atoi(inputstr)
改为
input, _ := strconv.Atoi(inputstr)
现在这个程序可以编译通过，没有任何错误。然而，当我运行程序时，我得到了以下结果：
Say something, in numbers.
0
然后程序就退出了...我做错了什么？我认为这是关于Atoi()方法的问题，但如果是关于Scanln()的问题，请纠正我。
英文:
I am trying to get a user input in this small program. I have tried doing this several ways with the strconv.Atoi() method (my input is obviously a string, and I'm trying to convert it to an integer). Here's my first attempt:
package main
import (
"fmt"
"strconv"
)
func main() {
//fmt.Println(strconv.Itoa)
fmt.Println("Say something, in numbers.")
var inputstr string
fmt.Scanln("%s", &inputstr)
input := strconv.Atoi(inputstr)
output := (input * 2)
outputstr := strconv.Itoa(output)
fmt.Println(outputstr)
}
and got the following error when it came to compiling:
> (line 19) multiple-value strconv.Atoi() in single-value context
I then looked into Godocs and tried to figure this out for myself, and then realized that an error value is returned as well. So, I changed the
input := strconv.Atoi(inputstr)
to
input, _ := strconv.Atoi(inputstr)
Now this compiles just fine, without any errors. However, when I run the program, here's what I get:
>Say something, in numbers.
>
>0
and then it exits... What am I doing wrong? I believe this is a question about to Atoi() method, but if it's concerning the Scanln() then please correct me.
答案1
得分: 11
问题的原因是Scanln函数。Scanln返回一个错误type not a pointer，这是因为使用了%s。这导致inputstr为空，当传递给Atoi函数时，会返回错误：strconv.ParseInt: parsing "": invalid syntax。
可以使用以下方式使用Scanf函数，而不对Atoi函数进行任何更改：
func main() {
//fmt.Println(strconv.Itoa)
fmt.Println("Say something, in numbers.")
var inputstr string
//fmt.Scanln("%s", &inputstr)
_, err := fmt.Scanf("%s", &inputstr)
if err != nil {
fmt.Println(err)
}
input, e := strconv.Atoi(inputstr)
if e != nil {
fmt.Println(e)
}
output := (input * 2)
outputstr := strconv.Itoa(output)
fmt.Println(outputstr)
}
可能最简单的解决方案是从Scanln函数中删除"%s"。
英文:
The problem turns out to be the Scanln. Scanln is returning an error type not a pointer because of the %s. This then leaves inputstr blank, which when given to Atoi is returning an error: strconv.ParseInt: parsing "": invalid syntax.
Using Scanf as follows with no change to the Atoi:
func main() {
//fmt.Println(strconv.Itoa)
fmt.Println("Say something, in numbers.")
var inputstr string
//fmt.Scanln("%s", &inputstr)
_, err := fmt.Scanf("%s", &inputstr)
if err != nil {
fmt.Println(err)
}
input, e := strconv.Atoi(inputstr)
if e != nil {
fmt.Println(e)
}
output := (input * 2)
outputstr := strconv.Itoa(output)
fmt.Println(outputstr)
}
Probably the simplest solution is to remove the "%s" from the Scanln.
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