1
考慮下面這個簡單的圍棋程序函數是否必須滿足函數類型的確切簽名?
package main
import (
"io"
"encoding/json"
"os"
)
type MyEncoder interface {
Encode(v interface{}) error
}
type MyEncoderCreator func(io.Writer) *MyEncoder
type MyContainer struct {
Creator MyEncoderCreator
}
func main() {
container := Container{
Creator:json.NewEncoder,
}
encoder := container.Creator(os.Stdout)
encoder.Encode(map[string]string{"key":"value"})
}
這項計劃失敗,出現以下錯誤編譯:
./main.go:21: cannot use json.NewEncoder (type func(io.Writer) *json.Encoder) as type MyEncoderCreator in field value
這是爲什麼? json.Encoder
結構具有滿足接口MyEncoder
的接收器。所以json.NewEncoder
函數應該被允許分配給MyContainer.Creator
?