[lectures/02-interfaces] Add defer and recover slides.

lectures/02-interfaces/copyfile/copy.go

@@ -0,0 +1,23 @@
+package copyfile
+
+import (
+	"io"
+	"os"
+)
+
+func CopyFile(dstName, srcName string) (written int64, err error) {
+	src, err := os.Open(srcName)
+	if err != nil {
+		return
+	}
+
+	dst, err := os.Create(dstName)
+	if err != nil {
+		return
+	}
+
+	written, err = io.Copy(dst, src)
+	dst.Close()
+	src.Close()
+	return
+}

lectures/02-interfaces/copyfile2/copy.go

@@ -0,0 +1,22 @@
+package copyfile2
+
+import (
+	"io"
+	"os"
+)
+
+func CopyFile(dstName, srcName string) (written int64, err error) {
+	src, err := os.Open(srcName)
+	if err != nil {
+		return
+	}
+	defer src.Close()
+
+	dst, err := os.Create(dstName)
+	if err != nil {
+		return
+	}
+	defer dst.Close()
+
+	return io.Copy(dst, src)
+}

lectures/02-interfaces/lecture.slide

@@ -411,6 +411,52 @@ Check type
       x.elements = nil
   }
 
+* defer
+
+.play copyfile/copy.go /func/,/^}/
+
+* defer
+
+.play copyfile2/copy.go /func/,/^}/
+
+* defer
+
+  func a() {
+      i := 0
+      defer fmt.Println(i)
+      i++
+      return
+  }
+
+Output:
+
+  0
+
+* defer
+
+  func b() {
+      for i := 0; i < 4; i++ {
+          defer fmt.Print(i)
+      }
+  }
+
+Output:
+
+  3210
+
+* defer
+
+  func c() (i int) {
+      defer func() { i++ }()
+      return 1
+  }
+
+  fmt.Println(c())
+
+Output:
+
+  2
+
 * defer
 
   func main() {
@@ -443,6 +489,31 @@ Output:
       // ...parser...
   }
 
+
+* recover
+
+  func main() {
+      defer func() {
+          recover()
+          fmt.Println("Checkpoint 1")
+          panic(1)
+      }()
+      defer func() {
+          recover()
+          fmt.Println("Checkpoint 2")
+          panic(2)
+      }()
+      panic(999)
+  }
+
+Output:
+
+  Checkpoint 2
+  Checkpoint 1
+  panic: 999 [recovered]
+  	panic: 2 [recovered]
+  	panic: 1
+
 * errors
 
   type error interface {