Add examples & exercise 7.02 of chapter 07

chapter_07/example_1/data.json

@@ -0,0 +1,4 @@
+{
+    "Name": "Torsten",
+    "Age": 41
+}

chapter_07/example_1/main.go

@@ -0,0 +1,65 @@
+package main
+
+import (
+  "encoding/json"
+  "fmt"
+  "io"
+  "os"
+  "strings"
+)
+
+type Person struct {
+  Name string `json:"name"`
+  Age  int    `json:"age"`
+}
+
+func loadPerson2(s string) (Person, error) {
+
+  var p Person
+  err := json.NewDecoder(strings.NewReader(s)).Decode(&p)
+  if err != nil {
+    return p, err
+  }
+  return p, nil
+
+}
+
+func loadPerson(r io.Reader) (Person, error) {
+
+  var p Person
+  err := json.NewDecoder(r).Decode(&p)
+  if err != nil {
+    return p, err
+  }
+  return p, nil
+
+}
+
+func main() {
+
+  s := `{"Name":"Joe","Age":18}`
+  s2 := `{"Name":"Jane","Age":21}`
+
+  p, err := loadPerson(strings.NewReader(s))
+  if err != nil {
+    fmt.Println(err)
+  }
+  fmt.Println(p)
+
+  p2, err := loadPerson2(s2)
+  if err != nil {
+    fmt.Println(err)
+  }
+  fmt.Println(p2)
+
+  f, err := os.Open("data.json")
+  if err != nil {
+    fmt.Println(err)
+  }
+  p3, err := loadPerson(f)
+  if err != nil {
+    fmt.Println(err)
+  }
+  fmt.Println(p3)
+
+}

chapter_07/example_2/main.go

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+package main
+
+import "fmt"
+
+type Speaker interface {
+  Speak() string
+}
+
+type cat struct {
+  name string
+}
+
+func catDetails(c cat) {
+  fmt.Printf("(%v, %T)\n", c, c)
+}
+
+func emptyDetails(s interface{}) {
+  fmt.Printf("(%v, %T)\n", s, s)
+}
+
+func main() {
+
+  c := cat{"oreo"}
+  i := 99
+  b := false
+  str := "test"
+  catDetails(c)
+  emptyDetails(c)
+  emptyDetails(i)
+  emptyDetails(b)
+  emptyDetails(str)
+
+}

chapter_07/example_3/main.go

@@ -0,0 +1,31 @@
+package main
+
+import "fmt"
+
+type cat struct {
+  name string
+}
+
+func typeExample(i []interface{}) {
+
+  for _, x := range i {
+    switch v := x.(type) {
+    case int:
+      fmt.Printf("%v is an int\n", v)
+    case string:
+      fmt.Printf("%v is a string\n", v)
+    case bool:
+      fmt.Printf("%v is a boolean\n", v)
+    default:
+      fmt.Printf("Unknown type %T\n", v)
+    }
+  }
+}
+
+func main() {
+
+  c := cat{"oreo"}
+  i := []interface{}{42, "The book club", true, c}
+  typeExample(i)
+
+}

chapter_07/exercise_7.03/main.go

@@ -0,0 +1,72 @@
+package main
+
+import "fmt"
+
+type record struct {
+  key       string
+  valueType string
+  data      interface{}
+}
+
+type person struct {
+  lastName  string
+  age       int
+  isMarried bool
+}
+
+type animal struct {
+  name     string
+  category string
+}
+
+func newRecord(key string, i interface{}) record {
+
+  r := record{}
+  r.key = key
+
+  switch v := i.(type) {
+  case int:
+    r.valueType = "int"
+    r.data = v
+  case bool:
+    r.valueType = "bool"
+    r.data = v
+  case string:
+    r.valueType = "string"
+    r.data = v
+  case person:
+    r.valueType = "person"
+    r.data = v
+  default:
+    r.valueType = "unknown"
+    r.data = v
+  }
+  return r
+
+}
+
+func main() {
+
+  m := make(map[string]interface{})
+  a := animal{name: "oreo", category: "cat"}
+  p := person{lastName: "Doe", isMarried: false, age: 19}
+  m["person"] = p
+  m["animal"] = a
+  m["age"] = 54
+  m["isMarried"] = true
+  m["lastName"] = "Smith"
+
+  rs := []record{}
+  for k, v := range m {
+    r := newRecord(k, v)
+    rs = append(rs, r)
+  }
+
+  for _, v := range rs {
+    fmt.Println("Key:", v.key)
+    fmt.Println("Data:", v.data)
+    fmt.Println("Type:", v.valueType)
+    fmt.Println()
+  }
+
+}