英文:
Write a function that returns a slice of interfaces in Golang
问题
在Golang中，Scanner接口接受一个名为dest的参数，该参数可以是任意数量的interface{}：
// Scan将当前行中的列复制到dest指向的值中。
func (rs *Rows) Scan(dest ...interface{}) error
是否有一种替代函数可以将接口的切片作为其结果返回？比如说，我想将dest参数放在一个函数中，这样我就不必每次都写出它们。
func scanArgs() []interface{} {
}
func main() {
db.QueryRow("SELECT * FROM users").Scan(scanArgs()...)
}
我尝试过这个方法，但是在方法签名方面遇到了问题；我可以将[]interface{}设置为返回值，但是在函数内部很难创建一个这样的切片。有没有更好的方法来实现这个？
英文:
In Golang the Scanner interface takes a single dest argument, which is any number of interface{}s:
// Scan copies the columns in the current row into the values pointed at by dest.
func (rs *Rows) Scan(dest ...interface{}) error
Is there an alternative function that can return a slice of interfaces as its result? Say I wanted to put the dest arguments in a function, so I didn't have to write them out every time.
func scanArgs() []interface{} {
}
func main() {
db.QueryRow("SELECT * FROM users").Scan(scanArgs()...)
}
I've tried this but I'm running into issues with the method signature; I can set a []interface as the return value, but I can't easily create one inside the function. Is there a better way to do this?
答案1
得分: 1
你可以使用以下语法在函数内部轻松分配内存：
package main
import "fmt"
func main() {
objs := &[]interface{}{}
objs2 := make([]interface{}, 10)
objs3 := []interface{}{}
fmt.Println(len(*objs))
fmt.Println(len(objs2))
fmt.Println(len(objs3))
}
由于所有类型都实现了空接口，你可以使用append将任何类型添加到这些集合中。初始化语法可能有点笨拙，可能会让你感到困惑...之所以看起来像那样，是因为我在那里声明了类型interface{}，通常你会有一个实际接口的名称，比如[]io.Writer{}。而在这种情况下，你需要使用这些额外的花括号。
英文:
You can easily allocate inside the function with syntax like the following;
package main
import "fmt"
func main() {
objs := &[]interface{}{}
objs2 := make([]interface{}, 10)
objs3 := []interface{}{}
fmt.Println(len(*objs))
fmt.Println(len(objs2))
fmt.Println(len(objs3))
}
Since everything implements the empty interface you can add any type to those collections with append. The init syntax is a bit clunky and probably what's throwing you... The reason it looks like that is because I'm declaring the type interface{} there when typically you'd have the name of an actual interface like []io.Writer{}. Instead you need those extract curlys.
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