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package main
import (
"fmt"
"io"
"os"
)
type WriteSyncer interface {
io.Writer
Sync() error
}
type Sink interface {
WriteSyncer
io.Closer
}
func newFileSink(path string) (Sink, error) {
return os.OpenFile(path, os.O_WRONLY|os.O_APPEND|os.O_CREATE, 0666)
}
type Sink1 struct{ name string }
func (s Sink1) Write(b []byte) (int, error) { println("in Write"); return 0, nil }
func (s Sink1) Sync() error { println("in Sync"); return nil }
func (s Sink1) Close() error { println("in Close", s.name); return nil }
func newS1(name string) Sink { return Sink1{name} }
func newS1p(name string) Sink { return &Sink1{name} }
type Sink2 struct{ name string }
func (s *Sink2) Write(b []byte) (int, error) { println("in Write"); return 0, nil }
func (s *Sink2) Sync() error { println("in Sync"); return nil }
func (s *Sink2) Close() error { println("in Close", s.name); return nil }
func newS2(name string) Sink { return Sink1{name} }
func main() {
tmpfile, err := os.CreateTemp("", "xxx")
if err != nil {
panic(err)
}
defer os.Remove(tmpfile.Name())
closers := []io.Closer{}
sink, err := newFileSink(tmpfile.Name())
if err != nil {
panic(err)
}
closers = append(closers, sink)
s1p := newS1p("ptr")
s1 := newS1("struct")
s2 := newS2("ptr2")
closers = append(closers, s1p, s1, s2)
for _, closer := range closers {
fmt.Println(closer.Close())
}
}
// Output:
// <nil>
// in Close ptr
// <nil>
// in Close struct
// <nil>
// in Close ptr2
// <nil>
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