英文:
How can I check the first character of a scanned string even if it is empty?
问题
我想让用户能够输入内容，并检查第一个字符是否为a，但如果他们将字符串留空，则会出现以下错误：
panic: runtime error: index out of range [0] with length 0
我的代码如下：
package mainimport "fmt"func main() {var a string;fmt.Scanln(&a);if string(a[0]) == "a" {fmt.Println("if true");}}
英文:
I want to have the user be able to put in input and check to see if the first character is an a but if they leave the string empty then it will cause the following error:
panic: runtime error: index out of range [0] with length 0
My code looks like:
package mainimport "fmt"func main() {var a string;fmt.Scanln(&a);if string(a[0]) == "a" {fmt.Println("if true");}}
答案1
得分: 3
一种方法是只检查第一个字符是否为"a"
var a stringfmt.Scanln(&a)if len(a) > 0 && string(a[0]) == "a" {fmt.Println("if true")}
另一种方法可以处理前导空格，例如当Scanln的输入为" a"时：
var a stringfmt.Scanln(&a)if strings.HasPrefix(a, "a") {fmt.Println("if true")}
英文:
One way to do it, will only check if the first character is "a"
var a string;fmt.Scanln(&a);if len(a) > 0 && string(a[0]) == "a" {fmt.Println("if true")}
Another, will work with leading spaces, for example when the input to Scanln is " a":
var a string;fmt.Scanln(&a);if strings.HasPrefix(a, "a") {fmt.Println("if true")}
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