英文:
Why does my code jump straight to default? Switch case in Go
问题
我刚开始学习Go，并尝试实现switch语句。据我所知，在其他语言中，这个语句需要使用"break;"，但在Go中不需要。不知何故，我的代码直接跳转到了default块。截至我写这个问题的时间，是2022年4月23日，星期六。
附言：如果有人能向我推荐一些可以免费学习Go的平台，我将不胜感激。
这是我的代码：
package main
import (
"fmt"
"time"
)
func main() {
fmt.Println("星期天是哪天？")
today := time.Now().Weekday()
switch time.Sunday {
case today + 0:
fmt.Println("今天。")
case today + 1:
fmt.Println("明天。")
case today + 2:
fmt.Println("后天。")
default:
fmt.Println("还有很长时间。")
}
}
英文:
I am just starting Go and tried implementing switch statement. As far as I know this statement in other languages require "break;" but not in Go. Somehow my code jumps directly into default block. By the time I am writing this question, it is 23/04/2022, Saturday.
P.S. I would be grateful if any of you could suggest me any platforms, where I can take Go courses for free.
This is my code:
package main
import (
"fmt"
"time"
)
func main() {
fmt.Println("when is Sunday?")
today := time.Now().Weekday()
switch time.Sunday {
case today + 0:
fmt.Println("Today.")
case today + 1:
fmt.Println("Tommorow.")
case today + 2:
fmt.Println("In 2 days.")
default:
fmt.Println("Too far away.")
}
}
答案1
得分: 2
time.Sunday 是一个值为0的常量。在你的switch语句中，你将1或2加到today上，但是当它达到6（星期六）时，值不会循环回到零。
所以你的switch语句的第二个和第三个条件永远不会成立。
下面的代码可以实现你的需求：
package main
import (
"fmt"
"time"
)
func main() {
fmt.Println("星期天是哪天？")
today := time.Now().Weekday()
switch today {
case time.Sunday:
fmt.Println("今天。")
case time.Saturday:
fmt.Println("明天。")
case time.Friday:
fmt.Println("后天。")
default:
fmt.Println("还有很长时间。")
}
}
英文:
time.Sunday is a const with the value 0. In your switch you add 1 or 2 to today but the value doesn't loop back around to zero after it reaches a value of 6 (Satureday).
So the second and third clause of your switch will never be true.
This does what you want:
package main
import (
"fmt"
"time"
)
func main() {
fmt.Println("when is Sunday?")
today := time.Now().Weekday()
switch today {
case time.Sunday:
fmt.Println("Today.")
case time.Saturday:
fmt.Println("Tommorow.")
case time.Friday:
fmt.Println("In 2 days.")
default:
fmt.Println("Too far away.")
}
}
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