reflect: MethodByName
It's more common to ask for methods by name than by index, so might
as well make it easy to do so.
R=rsc
CC=golang-dev
https://golang.org/cl/4639083
diff --git a/src/pkg/reflect/all_test.go b/src/pkg/reflect/all_test.go
index c83a9b7..94b0fb5 100644
--- a/src/pkg/reflect/all_test.go
+++ b/src/pkg/reflect/all_test.go
@@ -1050,6 +1050,12 @@
x, y int
}
+// This will be index 0.
+func (p Point) AnotherMethod(scale int) int {
+ return -1
+}
+
+// This will be index 1.
func (p Point) Dist(scale int) int {
// println("Point.Dist", p.x, p.y, scale)
return p.x*p.x*scale + p.y*p.y*scale
@@ -1058,26 +1064,52 @@
func TestMethod(t *testing.T) {
// Non-curried method of type.
p := Point{3, 4}
- i := TypeOf(p).Method(0).Func.Call([]Value{ValueOf(p), ValueOf(10)})[0].Int()
+ i := TypeOf(p).Method(1).Func.Call([]Value{ValueOf(p), ValueOf(10)})[0].Int()
if i != 250 {
t.Errorf("Type Method returned %d; want 250", i)
}
- i = TypeOf(&p).Method(0).Func.Call([]Value{ValueOf(&p), ValueOf(10)})[0].Int()
+ m, ok := TypeOf(p).MethodByName("Dist")
+ if !ok {
+ t.Fatalf("method by name failed")
+ }
+ m.Func.Call([]Value{ValueOf(p), ValueOf(10)})[0].Int()
+ if i != 250 {
+ t.Errorf("Type MethodByName returned %d; want 250", i)
+ }
+
+ i = TypeOf(&p).Method(1).Func.Call([]Value{ValueOf(&p), ValueOf(10)})[0].Int()
if i != 250 {
t.Errorf("Pointer Type Method returned %d; want 250", i)
}
+ m, ok = TypeOf(&p).MethodByName("Dist")
+ if !ok {
+ t.Fatalf("ptr method by name failed")
+ }
+ i = m.Func.Call([]Value{ValueOf(&p), ValueOf(10)})[0].Int()
+ if i != 250 {
+ t.Errorf("Pointer Type MethodByName returned %d; want 250", i)
+ }
+
// Curried method of value.
- i = ValueOf(p).Method(0).Call([]Value{ValueOf(10)})[0].Int()
+ i = ValueOf(p).Method(1).Call([]Value{ValueOf(10)})[0].Int()
if i != 250 {
t.Errorf("Value Method returned %d; want 250", i)
}
+ i = ValueOf(p).MethodByName("Dist").Call([]Value{ValueOf(10)})[0].Int()
+ if i != 250 {
+ t.Errorf("Value MethodByName returned %d; want 250", i)
+ }
// Curried method of pointer.
- i = ValueOf(&p).Method(0).Call([]Value{ValueOf(10)})[0].Int()
+ i = ValueOf(&p).Method(1).Call([]Value{ValueOf(10)})[0].Int()
if i != 250 {
- t.Errorf("Value Method returned %d; want 250", i)
+ t.Errorf("Pointer Value Method returned %d; want 250", i)
+ }
+ i = ValueOf(&p).MethodByName("Dist").Call([]Value{ValueOf(10)})[0].Int()
+ if i != 250 {
+ t.Errorf("Pointer Value MethodByName returned %d; want 250", i)
}
// Curried method of interface value.
@@ -1094,6 +1126,10 @@
if i != 250 {
t.Errorf("Interface Method returned %d; want 250", i)
}
+ i = pv.MethodByName("Dist").Call([]Value{ValueOf(10)})[0].Int()
+ if i != 250 {
+ t.Errorf("Interface MethodByName returned %d; want 250", i)
+ }
}
func TestInterfaceSet(t *testing.T) {
diff --git a/src/pkg/reflect/type.go b/src/pkg/reflect/type.go
index 6c1ab60..f774f73 100644
--- a/src/pkg/reflect/type.go
+++ b/src/pkg/reflect/type.go
@@ -47,6 +47,16 @@
// method signature, without a receiver, and the Func field is nil.
Method(int) Method
+ // MethodByName returns the method with that name in the type's
+ // method set and a boolean indicating if the method was found.
+ //
+ // For a non-interface type T or *T, the returned Method's Type and Func
+ // fields describe a function whose first argument is the receiver.
+ //
+ // For an interface type, the returned Method's Type field gives the
+ // method signature, without a receiver, and the Func field is nil.
+ MethodByName(string) (Method, bool)
+
// NumMethod returns the number of methods in the type's method set.
NumMethod() int
@@ -344,6 +354,7 @@
Name string
Type Type
Func Value
+ Index int
}
// High bit says whether type has
@@ -451,6 +462,7 @@
m.Type = toType(p.typ)
fn := p.tfn
m.Func = valueFromIword(flag, m.Type, iword(fn))
+ m.Index = i
return
}
@@ -461,6 +473,20 @@
return len(t.methods)
}
+func (t *uncommonType) MethodByName(name string) (m Method, ok bool) {
+ if t == nil {
+ return
+ }
+ var p *method
+ for i := range t.methods {
+ p = &t.methods[i]
+ if p.name != nil && *p.name == name {
+ return t.Method(i), true
+ }
+ }
+ return
+}
+
// TODO(rsc): 6g supplies these, but they are not
// as efficient as they could be: they have commonType
// as the receiver instead of *commonType.
@@ -480,6 +506,14 @@
return t.uncommonType.Method(i)
}
+func (t *commonType) MethodByName(name string) (m Method, ok bool) {
+ if t.Kind() == Interface {
+ tt := (*interfaceType)(unsafe.Pointer(t))
+ return tt.MethodByName(name)
+ }
+ return t.uncommonType.MethodByName(name)
+}
+
func (t *commonType) PkgPath() string {
return t.uncommonType.PkgPath()
}
@@ -636,12 +670,28 @@
m.PkgPath = *p.pkgPath
}
m.Type = toType(p.typ)
+ m.Index = i
return
}
// NumMethod returns the number of interface methods in the type's method set.
func (t *interfaceType) NumMethod() int { return len(t.methods) }
+// MethodByName method with the given name in the type's method set.
+func (t *interfaceType) MethodByName(name string) (m Method, ok bool) {
+ if t == nil {
+ return
+ }
+ var p *imethod
+ for i := range t.methods {
+ p = &t.methods[i]
+ if *p.name == name {
+ return t.Method(i), true
+ }
+ }
+ return
+}
+
type StructField struct {
PkgPath string // empty for uppercase Name
Name string
diff --git a/src/pkg/reflect/value.go b/src/pkg/reflect/value.go
index b1999aa..889d945 100644
--- a/src/pkg/reflect/value.go
+++ b/src/pkg/reflect/value.go
@@ -1023,6 +1023,23 @@
return Value{v.Internal, i + 1}
}
+// MethodByName returns a function value corresponding to the method
+// of v with the given name.
+// The arguments to a Call on the returned function should not include
+// a receiver; the returned function will always use v as the receiver.
+// It returns the zero Value if no method was found.
+func (v Value) MethodByName(name string) Value {
+ iv := v.internal()
+ if iv.kind == Invalid {
+ panic(&ValueError{"reflect.Value.MethodByName", Invalid})
+ }
+ m, ok := iv.typ.MethodByName(name)
+ if ok {
+ return Value{v.Internal, m.Index + 1}
+ }
+ return Value{}
+}
+
// NumField returns the number of fields in the struct v.
// It panics if v's Kind is not Struct.
func (v Value) NumField() int {
