defer先進後出
舉例:
package main
import (
"fmt"
"os"
"bufio"
)
//打開文件
func writeFile(filename string) {
file, err := os.Create(filename)
if err != nil {
panic(err)
}
//往文件寫內容(直接寫文件會比較慢,所以這裏用bufio。先寫到內存裏,再內存一下寫進去會比較快)
writer := bufio.NewWriter(file)
for i := 0; i < 20; i++ {
fmt.Fprintln(writer, i)
}
defer file.Close()
defer writer.Flush()
}
func main() {
//tryDefer()
writeFile("haha.txt")
}
先執行writer.Flush(),再執行file.Close()。反之不能寫入