reflectx

reflectx

Golang reflect package hack tools

struct unexported field can set

• reflectx.CanSet
• reflectx.Field
• reflectx.FieldByIndex
• reflectx.FieldByName
• reflectx.FieldByNameFunc

type Point struct {
    x int
    y int
}

x := &Point{10, 20}
v := reflect.ValueOf(x).Elem()
sf := v.Field(0)

fmt.Println(sf.CanSet()) // output: false
// sf.SetInt(102)        
// panic: reflect: reflect.Value.SetInt using value obtained using unexported field

sf = reflectx.CanSet(sf)
fmt.Println(sf.CanSet()) // output: true

sf.SetInt(102)           // x.x = 102
fmt.Println(x.x)         // output: 102

reflectx.Field(x,1).SetInt(100) // x.y = 100

embedded type more than one field

• reflectx.StructOf

type Buffer struct {
	*bytes.Buffer
	X int
	Y int
}

typ := reflect.TypeOf((*Buffer)(nil)).Elem()
var fs []reflect.StructField
for i := 0; i < typ.NumField(); i++ {
	fs = append(fs, typ.Field(i))
}

// reflect.StructOf(fs) 
// panic reflect: embedded type with methods not implemented if there is more than one field

reflectx.StructOf(fs)

different types of fields generated by name

• reflectx.NamedStructOf

fs := []reflect.StructField{
	reflect.StructField{Name: "X", Type: reflect.TypeOf(0)},
	reflect.StructField{Name: "Y", Type: reflect.TypeOf(0)},
}
t1 := reflectx.NamedStructOf("Point", fs)
t2 := reflectx.NamedStructOf("Point", fs)
t3 := reflectx.NamedStructOf("Point2", fs)

// t1 == t2
// t1 != t3