feat(json): 添加 JSON 编码示例和折扣产品结构

- 新增 DiscountedProduct 和 DiscountedProductChange 结构体
- 实现 mainJson 函数，包含多个 JSON 编码示例
- 更新 Product 结构体字段名称为导出形式
- 添加 mainJson1 到 mainJson7 的具体编码演示
-修复结构体标签和 JSON 序列化相关问题

20-readersandwriters/readersandwriters/discount.go

@@ -0,0 +1,13 @@
+package main
+
+type DiscountedProduct struct {
+	// *Product
+	*Product `json:",omitempty"`
+	Discount float64 `json:",string"`
+}
+
+type DiscountedProductChange struct {
+	// *Product `json:"product"`
+	*Product `json:"product,omitempty"`
+	Discount float64 `json:"-"`
+}

20-readersandwriters/readersandwriters/main.go

@@ -16,6 +16,7 @@ func main() {
 	main7()
 	main8()
 	main9()
+	mainJson()
 }
 
 func main1() {

20-readersandwriters/readersandwriters/mainJson.go

@@ -0,0 +1,230 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"io"
+	"strings"
+)
+
+func mainJson() {
+	mainJson1()
+	mainJson2()
+	mainJson3()
+	mainJson4()
+	mainJson5()
+	mainJson6()
+	mainJson7()
+	mainJson8()
+	mainJson9()
+	mainJson10()
+	mainJson11()
+}
+
+func mainJson1() {
+	Printfln("\nmainJson1")
+	b := true
+	str := "hello"
+	fVal := 99.99
+	iVal := 200
+	pointer := &iVal
+
+	var writer strings.Builder
+	encoder := json.NewEncoder(&writer)
+
+	for _, val := range []interface{}{b, str, fVal, iVal, pointer} {
+		err := encoder.Encode(val)
+		if err != nil {
+			Printfln("Error: %v", err.Error())
+			return
+		}
+	}
+	fmt.Println(writer.String())
+}
+
+func mainJson2() {
+	Printfln("\nmainJson2")
+
+	names := []string{"Kayak", "Lifejacket", "Soccer Ball"}
+	numbers := [3]int{1, 2, 3}
+	numberSlice := []int{1, 2, 3}
+	var byteArray [5]byte
+	copy(byteArray[0:], []byte(names[0]))
+	byteSlice := []byte(names[0])
+
+	var writer strings.Builder
+	encoder := json.NewEncoder(&writer)
+
+	encoder.Encode(names)
+	encoder.Encode(numbers)
+	encoder.Encode(numberSlice)
+	encoder.Encode(byteArray)
+	encoder.Encode(byteSlice)
+
+	fmt.Println(writer.String())
+}
+
+func mainJson3() {
+	Printfln("\nmainJson3")
+	m := map[string]float64{
+		"Kayak":      275,
+		"Lifejacket": 48.95,
+	}
+
+	var writer strings.Builder
+	encoder := json.NewEncoder(&writer)
+	encoder.Encode(m)
+	fmt.Println(writer.String())
+}
+
+func mainJson4() {
+	Printfln("\nmainJson4")
+
+	var writer strings.Builder
+	encoder := json.NewEncoder(&writer)
+	encoder.Encode(&Kayak)
+	fmt.Println(writer.String())
+}
+func mainJson5() {
+	Printfln("\nmainJson5")
+	var writer strings.Builder
+	encoder := json.NewEncoder(&writer)
+
+	dp := DiscountedProduct{
+		Product:  &Kayak,
+		Discount: 10.50,
+	}
+	encoder.Encode(&dp)
+	fmt.Println(writer.String())
+}
+func mainJson6() {
+	Printfln("\nmainJson6")
+	var writer strings.Builder
+	encoder := json.NewEncoder(&writer)
+
+	dp := DiscountedProductChange{
+		Product:  &Kayak,
+		Discount: 10.50,
+	}
+	encoder.Encode(&dp)
+	fmt.Println(writer.String())
+}
+
+func mainJson7() {
+	Printfln("\nmainJson7")
+	var writer strings.Builder
+	encoder := json.NewEncoder(&writer)
+
+	dp := DiscountedProductChange{
+		Product:  &Kayak,
+		Discount: 10.50,
+	}
+	encoder.Encode(&dp)
+
+	dp2 := DiscountedProductChange{
+		Discount: 10.50,
+	}
+	encoder.Encode(&dp2)
+
+	dp3 := DiscountedProduct{
+		Discount: 10.50,
+	}
+	encoder.Encode(&dp3)
+
+	fmt.Println(writer.String())
+}
+
+func mainJson8() {
+	Printfln("\nmainJson8")
+
+	reader := strings.NewReader(`{"Kayak":279,"Lifejacket":49.95}`)
+
+	m := map[string]interface{}{}
+
+	decoder := json.NewDecoder(reader)
+
+	err := decoder.Decode(&m)
+	if err != nil {
+		Printfln("Error: %v", err.Error())
+	} else {
+		Printfln("Map: %T , %v", m, m)
+		for key, value := range m {
+			Printfln("Key: %v, Value: %v", key, value)
+		}
+
+		Printfln("Kayak: %v", m["Kayak"])
+		Printfln("Lifejacket: %v", m["Lifejacket"])
+	}
+}
+
+func mainJson9() {
+	Printfln("\nmainJson9")
+
+	reader := strings.NewReader(`{"Kayak":279,"Lifejacket":49.95}`)
+
+	m := map[string]float64{}
+
+	decoder := json.NewDecoder(reader)
+
+	err := decoder.Decode(&m)
+	if err != nil {
+		Printfln("Error: %v", err.Error())
+	} else {
+		Printfln("Map: %T , %v", m, m)
+		for key, value := range m {
+			Printfln("Key: %v, Value: %v", key, value)
+		}
+
+		Printfln("Kayak: %v", m["Kayak"])
+		Printfln("Lifejacket: %v", m["Lifejacket"])
+	}
+}
+
+func mainJson10() {
+	Printfln("\nmainJson10")
+	reader := strings.NewReader(`
+       { "Name": "Kayak" , "Category": "Watersports","Price":270}
+       { "Name": "Lifejacket" , "Category": "Watersports" }
+       { "name": "Canoe" , "category": "Watersports" , "price" : 100 , "inStock" : true }
+`)
+	decoder := json.NewDecoder(reader)
+
+	for {
+		var val Product
+		err := decoder.Decode(&val)
+		if err != nil {
+			if err == io.EOF {
+				break
+			}
+			Printfln("Error: %v", err.Error())
+			break
+		} else {
+			Printfln("Name: %v, Category: %v, Price: %v", val.Name, val.Category, val.Price)
+		}
+	}
+}
+
+func mainJson11() {
+	Printfln("\nmainJson10")
+	reader := strings.NewReader(`
+       { "Name": "Kayak" , "Category": "Watersports","Price":270}
+       { "Name": "Lifejacket" , "Category": "Watersports" }
+       { "name": "Canoe" , "category": "Watersports" , "price" : 100 , "inStock" : true }
+`)
+	decoder := json.NewDecoder(reader)
+	decoder.DisallowUnknownFields()
+
+	for {
+		var val Product
+		err := decoder.Decode(&val)
+		if err != nil {
+			if err == io.EOF {
+				break
+			}
+			Printfln("Error: %v", err.Error())
+			break
+		} else {
+			Printfln("Name: %v, Category: %v, Price: %v", val.Name, val.Category, val.Price)
+		}
+	}
+}

20-readersandwriters/readersandwriters/product.go

@@ -1,13 +1,13 @@
 package main
 
 type Product struct {
-	Name, category string
+	Name, Category string
 	Price          float64
 }
 
 var Kayak = Product{
 	Name:     "Kayak",
-	category: "Watersports",
+	Category: "Watersports",
 	Price:    279,
 }
 

23-htmltext/htmltext/go.mod

@@ -0,0 +1,3 @@
+module htmltext
+
+go 1.22

23-htmltext/htmltext/main.go

@@ -0,0 +1,5 @@
+package main
+
+func main() {
+	Printfln("Product: %v Price: %v", Kayak.Name, Kayak.Price)
+}

23-htmltext/htmltext/printer.go

@@ -0,0 +1,7 @@
+package main
+
+import "fmt"
+
+func Printfln(template string, values ...interface{}) {
+	fmt.Printf(template+"\n", values...)
+}

23-htmltext/htmltext/product.go

@@ -0,0 +1,23 @@
+package main
+
+type Product struct {
+	Name, Category string
+	Price          float64
+}
+
+var Kayak = Product{
+	Name:     "Kayak",
+	Category: "Watersports",
+	Price:    279,
+}
+
+var ProductList = []Product{
+	{"Kayak", "Watersports", 279},
+	{"LifeJacket", "Watersports", 49.95},
+	{"Soccer Ball", "Soccer", 19.50},
+	{"Corner Flags", "Soccer", 34.95},
+	{"Stadium", "Soccer", 79500},
+	{"Thinking Cap", "Chess", 16},
+	{"Unsteady Chair", "Chess", 75},
+	{"Bling-Bling King", "Chess", 1200},
+}