feat(go): 添加反射和函数调用功能

- 新增 Find 函数用于在切片中查找匹配项
- 定义 NamedItem 和 CurrencyItem 接口及其实现
- 添加 Purchase 类型的方法 calcTax 和 calcTotal
- 实现 inspectFuncType、invokeFunction 和 mapSlice 反射工具函数
- 在 main28 中演示反射功能的使用
- 更新 main.go以调用 main28 函数

27-reflection/reflection/functions.go

@@ -0,0 +1,13 @@
+package main
+
+func Find(slice []string, vals ...string) (matches bool) {
+	for _, item := range slice {
+		for _, val := range vals {
+			if item == val {
+				matches = true
+				return
+			}
+		}
+	}
+	return
+}

27-reflection/reflection/interfaces.go

@@ -0,0 +1,32 @@
+package main
+
+import "fmt"
+
+type NamedItem interface {
+	GetName() string
+	unexportedMethod()
+}
+
+type CurrencyItem interface {
+	GetAmount() string
+	currencyName() string
+}
+
+func (p *Product) GetName() string {
+	return p.Name
+}
+
+func (p *Product) GetAmount() string {
+	return fmt.Sprintf("$%.2f", p.Price)
+}
+
+func (p *Product) currencyName() string {
+	return "USD"
+}
+
+func (p *Product) unexportedMethod() {
+}
+
+func (c *Customer) GetName() string {
+	return c.Name
+}

27-reflection/reflection/main.go

@@ -25,4 +25,6 @@ func main() {
 	main25()
 	main26()
 	main27()
+
+	main28()
 }

27-reflection/reflection/methods.go

@@ -0,0 +1,9 @@
+package main
+
+func (p Purchase) calcTax(taxRate float64) float64 {
+	return p.Price * taxRate
+}
+
+func (p Purchase) calcTotal() float64 {
+	return p.Price + p.calcTax(0.20)
+}

27-reflection/reflection/re3.go

@@ -0,0 +1,77 @@
+package main
+
+import (
+	"reflect"
+	"strings"
+)
+
+func inspectFuncType(f interface{}) {
+	Printfln("\ninspectFuncType:")
+	funcType := reflect.TypeOf(f)
+	if funcType.Kind() != reflect.Func {
+		Printfln("Not a function")
+		return
+	}
+	Printfln("Function parameters count: %v", funcType.NumIn())
+	for i := 0; i < funcType.NumIn(); i++ {
+		paramType := funcType.In(i)
+		if i < funcType.NumIn()-1 {
+			Printfln("Parameter #%v, Type: %v", i, paramType)
+		} else {
+			Printfln("Parameter #%v, Type: %v, Variadic: %v", i, paramType, funcType.IsVariadic())
+		}
+	}
+
+	Printfln("Function results count: %v", funcType.NumOut())
+	for i := 0; i < funcType.NumOut(); i++ {
+		resultType := funcType.Out(i)
+		Printfln("Result #%v, Type: %v", i, resultType)
+	}
+}
+
+func invokeFunction(f interface{}, params ...interface{}) {
+	Printfln("\ninvokeFunction:")
+	paramVals := []reflect.Value{}
+	for _, p := range params {
+		paramVals = append(paramVals, reflect.ValueOf(p))
+	}
+	funcVal := reflect.ValueOf(f)
+	if funcVal.Kind() == reflect.Func {
+		results := funcVal.Call(paramVals)
+		for i, result := range results {
+			Printfln("Result #%v: %v", i, result)
+		}
+	}
+}
+
+func mapSlice(slice interface{}, mapper interface{}) (mapped []interface{}) {
+	Printfln("\nmapSlice:")
+	sliceVal := reflect.ValueOf(slice)
+	mapperVal := reflect.ValueOf(mapper)
+	mapped = []interface{}{}
+	if sliceVal.Kind() == reflect.Slice &&
+		mapperVal.Kind() == reflect.Func &&
+		mapperVal.Type().NumIn() == 1 &&
+		// 函数参数0的参数类型等于数组元素的参数类型
+		mapperVal.Type().In(0) == sliceVal.Type().Elem() {
+		for i := 0; i < sliceVal.Len(); i++ {
+			result := mapperVal.Call([]reflect.Value{sliceVal.Index(i)})
+			for _, r := range result {
+				mapped = append(mapped, r.Interface())
+			}
+		}
+	}
+	return
+}
+
+func main28() {
+	Printfln("\nmain28:")
+
+	inspectFuncType(Find)
+
+	names := []string{"Alice", "Bob", "Charlie"}
+	invokeFunction(Find, names, "London", "Bob")
+
+	results := mapSlice(names, strings.ToUpper)
+	Printfln("Results: %v", results)
+}