From 907c9622a694c56211bad5b09e3d8d0e57cb3332 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E7=8B=AC=E5=AD=A4=E4=BC=B6=E4=BF=9C?= <1184662350@qq.com>
Date: Sun, 18 Dec 2022 21:10:53 +0800
Subject: [PATCH] =?UTF-8?q?day9=E6=8E=A5=E5=8F=A3=20=E7=B1=BB=E5=9E=8B?=
 =?UTF-8?q?=E6=96=AD=E8=A8=80?=
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---
 src/study/day9Interface/TypeAssertions.go | 31 +++++++++++++++++++++++
 1 file changed, 31 insertions(+)
 create mode 100644 src/study/day9Interface/TypeAssertions.go

diff --git a/src/study/day9Interface/TypeAssertions.go b/src/study/day9Interface/TypeAssertions.go
new file mode 100644
index 0000000..a30ffbf
--- /dev/null
+++ b/src/study/day9Interface/TypeAssertions.go
@@ -0,0 +1,31 @@
+package main
+
+import (
+	"fmt"
+	"io"
+	"os"
+)
+
+func main() {
+	// 类型断言
+
+	var w io.Writer
+	w = os.Stdout
+	f := w.(*os.File) // success: f == os.Stdout
+	//c := w.(*bytes.Buffer) // panic: interface holds *os.File, not *bytes.Buffer
+	fmt.Println(f)
+	rw := w.(io.ReadWriter)
+	w = rw
+	fmt.Printf("(%T, %[1]v)\n", w)
+	// 被断言的接口值的动态类型不能是nil，否则会引发panic
+	w = nil
+	// panic: interface conversion: interface {} is nil, not io.ReadWriter
+	//rw = w.(io.ReadWriter) /
+	fmt.Printf("(%T, %[1]v)\n", w)
+
+	// 判断断言是否成功可以使用comma-ok断言
+	w = os.Stdout
+	f, ok := w.(*os.File) // success: f == os.Stdout, ok == true
+	fmt.Println(ok)
+	f.WriteString("hello, world") // 向控制台输出hello, world
+}