英文:
How do I get the switch statement to work when there is an error in switch case
问题
根据用户从命令行输入的内容，switch case 语句根据一个整数返回评级。由于命令行参数的类型是字符串，我首先将其转换为 int，然后在 switch 语句中使用。
package main
import (
"fmt"
"os"
"reflect"
"strconv"
)
func main() {
rating, _ := strconv.Atoi(os.Args[1])
fmt.Println(reflect.TypeOf(rating))
switch {
case rating >= 2100:
fmt.Println("grand master")
case rating >= 1900:
fmt.Println("candidate master")
case rating >= 1600:
fmt.Println("expert")
case rating >= 1400:
fmt.Println("pupil")
case rating < 1400:
fmt.Println("newbie")
}
}
现在在 rating >= 2100 和其他所有比较中都存在错误。错误信息如下：
cannot convert rating >= 2100 (untyped bool value) to intcompilerInvalidUntypedConversion
我无法理解如何解决这个问题。
请帮忙解决！
英文:
based on user input from command line, switch case returns rating for an integer. Since command line arguments are of type string, I first convert it to int and then use it in switch.
package main
import (
"fmt"
"os"
"reflect"
"strconv"
)
func main() {
rating, _ := strconv.Atoi(os.Args[1])
fmt.Println(reflect.TypeOf(rating))
switch rating {
case rating >= 2100:
fmt.Println("grand master")
case rating >= 1900:
fmt.Println("candidate master")
case rating >= 1600:
fmt.Println("expert")
case rating >= 1400:
fmt.Println("pupil")
case rating < 1400:
fmt.Println("newbie")
}
}
Now there is error on rating >= 2100, for all comparisons rather. It goes as follows:
cannot convert rating >= 2100 (untyped bool value) to intcompilerInvalidUntypedConversion
Not able to understand how to resolve this.
Please help!
答案1
得分: 6
如果你使用switch表达式，你必须在可比较的地方使用case表达式。规范：Switch语句：
对于每个（可能转换的）case表达式
x和switch表达式的值t，x == t必须是一个有效的比较。
也就是说，如果你使用switch rating { ... }，那么你只需要指定整数值，例如2100，而不是像rating >= 2100这样的比较。
显然，你不想要单个值，而是范围，所以省略switch表达式：
switch {
case rating >= 2100:
fmt.Println("grand master")
case rating >= 1900:
fmt.Println("candidate master")
case rating >= 1600:
fmt.Println("expert")
case rating >= 1400:
fmt.Println("pupil")
case rating < 1400:
fmt.Println("newbie")
}
英文:
If you use a switch expression, you have to use case expressions where they are comparable. Spec: Switch statements:
> For each (possibly converted) case expression x and the value t of the switch expression, x == t must be a valid comparison.
That is, if you use switch rating { ... }, then you only need to specify the integer values, e.g. 2100, and not a comparison like rating >= 2100.
Obviously you don't want single values but ranges, so omit the switch expression:
switch {
case rating >= 2100:
fmt.Println("grand master")
case rating >= 1900:
fmt.Println("candidate master")
case rating >= 1600:
fmt.Println("expert")
case rating >= 1400:
fmt.Println("pupil")
case rating < 1400:
fmt.Println("newbie")
}
答案2
得分: 0
你只是在重复已经存在于上方的变量名。
英文:
you're basically repeating the variable name that already exists aboveenter image description here
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