英文:
Use int as month when constructing date
问题
当我将一个int作为time.Date的month参数传递时，它可以正常工作（示例）：
time.Date(2016, 1, 1, 0, 0, 0, 0, time.UTC)
但是，为什么当我尝试将一个string转换为int，然后使用该变量时，会出现以下错误：
cannot use mStr (type int) as type time.Month in argument to time.Date
示例：https://play.golang.org/p/-XFNZHK476
英文:
When I supply an int as an argument to time.Date for month, it works (Example):
time.Date(2016, 1, 1, 0, 0, 0, 0, time.UTC)
Why, when I try to convert a string to int and then use that variable, I get the error:
<!-- language: lang-none -->
cannot use mStr (type int) as type time.Month in argument to time.Date
Example: https://play.golang.org/p/-XFNZHK476
答案1
得分: 24
你需要将值转换为正确的类型：
import (
"fmt"
"time"
"strconv"
)
func main() {
var m, _ = strconv.Atoi("01")
// 现在将 m 转换为 time.Month 类型
fmt.Println(time.Date(2016, time.Month(m), 1, 0, 0, 0, 0, time.UTC))
}
你将其转换为了 int 类型，但是 time.Date() 的第二个参数是 time.Month 类型，所以它会给你一个错误，提示你没有使用正确的类型。
英文:
You have to convert the value to the proper type:
import(
"fmt"
"time"
"strconv"
)
func main() {
var m, _ = strconv.Atoi("01")
// Now convert m to type time.Month
fmt.Println(time.Date(2016, time.Month(m), 1, 0, 0, 0, 0, time.UTC))
}
You converted it to a type int, but the 2nd parameter of time.Date() is of type time.Month so it would give you an error that you are not using the correct type.
答案2
得分: 1
在第一个示例中，您将类型声明为time.Month，它不是int类型，而是time.Month类型。在第二个示例中，类型是int。如果您进行了类型转换，就像在这个示例中一样，它将按您的预期工作；https://play.golang.org/p/drD_7KiJu4
如果在您的第一个示例中，您将m声明为int类型，或者只是使用:=运算符（隐含类型为int），您将得到与第二个示例中相同的错误。在这里演示；https://play.golang.org/p/iWc-2Mpsly
英文:
In the first example you're declaring the type as a time.Month, it is not an int, it is a time.Month. In the second example the type is an int. If you were to do a cast, like in this example it would work as you expect; https://play.golang.org/p/drD_7KiJu4
If in your first example you declared m as an int or just used the := operator (the implied type would be int) and you would get the same error as in the second example. Demonstrated here; https://play.golang.org/p/iWc-2Mpsly
答案3
得分: 1
Go编译器只会自动将常量转换为相应的类型，变量需要显式进行类型转换。
英文:
The Go compiler only casts constants to types on its own. Variables need to be explicitly cast.
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