【golang/实验性】如何使用类型名进行实例化

说在前面

• go版本：go1.14.1 windows/amd64

问题提出

type XStruct strcut {
	Data	int
}

a := function("XStruct")
fmt.Println(a.Data)

其他语言

Class<?> clazz = Class.forName(className);
Constructor<?> ctor = clazz.getConstructor(String.class);
Object object = ctor.newInstance(new Object[] { ctorArgument });

注册式方法

type XStruct struct {
	Data int
}

type YStruct struct {
	Data string
}

var typeRegistry = make(map[string]reflect.Type)

// 注册
func Register() {
	typeList := []interface{}{
		&XStruct{},
		&YStruct{},
	}

	for idx := range typeList {
		inter := typeList[idx]
		typeRegistry[fmt.Sprintf("%T", inter)] = reflect.TypeOf(inter)
	}
}

func main() {
	Register()

	t, ok := typeRegistry["*main.XStruct"]
	if !ok {
		return
	}

	v := reflect.New(t)

	// 这个转换也太傻了
	s := (*XStruct)(unsafe.Pointer(v.Pointer()))
	s.Data = 1

	fmt.Println(s)
}

PS E:\Mscript> go run .\main.go
&{1}

注册式处理指针类型

type XStruct struct {
	Data int
}

func (this *XStruct) Out() {
	fmt.Println(this.Data)
}

type YStruct struct {
	Data string
}

var typeRegistry = make(map[string]reflect.Type)
var valRegistry = make(map[string]reflect.Value)

func Register() {
	typeList := []interface{}{
		new(XStruct),
		new(YStruct),
	}

	for idx := range typeList {
		inter := typeList[idx]
		typeRegistry[fmt.Sprintf("%T", inter)] = reflect.TypeOf(inter)
		valRegistry[fmt.Sprintf("%T", inter)] = reflect.ValueOf(inter)
	}
}

func main() {
	Register()

	t, ok := valRegistry["*main.XStruct"]
	if !ok {
		return
	}

	v := reflect.New(t.Type().Elem()).Interface()

	fmt.Println(v)
}

神奇的方法

|--common
	|--common.s
	|--handler.go
|--main.go

TEXT ·typelinks(SB), $0-0
    JMP reflect·typelinks(SB)

func Typelinks() (sections []unsafe.Pointer, offset [][]int32) {
	return typelinks()
}

func typelinks() (sections []unsafe.Pointer, offset [][]int32)

func Add(p unsafe.Pointer, x uintptr, whySafe string) unsafe.Pointer {
	return add(p, x, whySafe)
}

func add(p unsafe.Pointer, x uintptr, whySafe string) unsafe.Pointer {
	return unsafe.Pointer(uintptr(p) + x)
}

func main() {
	sections, offsets := common.Typelinks()
	for i, base := range sections {
		for _, offset := range offsets[i] {
			typeAddr := common.Add(base, uintptr(offset), "")
			typ := reflect.TypeOf(*(*interface{})(unsafe.Pointer(&typeAddr)))
			val := reflect.ValueOf(*(*interface{})(unsafe.Pointer(&typeAddr)))
			fmt.Println(typ, val)
		}
	}
}

struct { root runtime.semaRoot; pad [40]uint8 }
struct { runtime.gList; n int32 }
struct { runtime.mutex; runtime.persistentAlloc }
struct { scheme tls.SignatureScheme; minModulusBytes int; maxVersion uint16 }
struct { size uint32; nmalloc uint64; nfree uint64 }
struct { sync.Mutex; m sync.Map }
struct { sync.Mutex; table [64]big.divisor }
struct { sync.Once; val int }
struct { user bool; runnable runtime.gQueue; n int32 }
struct { v interface {}; tag string; l []string }
struct {}

接口调用

interface{}interface{}

参考