From 76482820f3615f4312c3f1b95fa458b69b6e4f23 Mon Sep 17 00:00:00 2001
From: shockerli <shockerli@upfor.club>
Date: Thu, 11 Mar 2021 17:04:39 +0800
Subject: [PATCH] add func FieldE

return the field value from map/struct, ignore the filed type
---
 cvte.go      | 24 ++++++++++++++++++++++++
 cvte_test.go | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 73 insertions(+)

diff --git a/cvte.go b/cvte.go
index e2f26bf..1d231a1 100644
--- a/cvte.go
+++ b/cvte.go
@@ -12,6 +12,7 @@ import (
 )
 
 var errConvFail = errors.New("convert failed")
+var errFieldNotFound = errors.New("field not found")
 var formatOutOfLimitInt = "%w, out of max limit value(%d)"
 var formatOutOfLimitFloat = "%w, out of max limit value(%f)"
 var formatExtend = "%v, %w"
@@ -392,6 +393,7 @@ func SliceE(val interface{}) (sl []interface{}, err error) {
 	return nil, newErr(val, "slice")
 }
 
+// return the values of struct fields, and deep find the embedded fields
 func deepStructValues(rt reflect.Type, rv reflect.Value) (sl []interface{}) {
 	for j := 0; j < rv.NumField(); j++ {
 		if rt.Field(j).Anonymous {
@@ -403,6 +405,28 @@ func deepStructValues(rt reflect.Type, rv reflect.Value) (sl []interface{}) {
 	return
 }
 
+// FieldE return the field value from map/struct, ignore the filed type
+func FieldE(val interface{}, field interface{}) (interface{}, error) {
+	sf := String(field) // match with the String of field, so field can be any type
+	_, rt, rv := Indirect(val)
+
+	switch rt.Kind() {
+	case reflect.Map: // key of map
+		for _, key := range rv.MapKeys() {
+			if String(key.Interface()) == sf {
+				return rv.MapIndex(key).Interface(), nil
+			}
+		}
+	case reflect.Struct: // field of struct
+		vv := rv.FieldByName(sf)
+		if vv.IsValid() {
+			return vv.Interface(), nil
+		}
+	}
+
+	return nil, fmt.Errorf("%w(%s)", errFieldNotFound, sf)
+}
+
 // Indirect returns the value with base type
 func Indirect(a interface{}) (val interface{}, rt reflect.Type, rv reflect.Value) {
 	if a == nil {
diff --git a/cvte_test.go b/cvte_test.go
index 2f98dc5..0682fe8 100644
--- a/cvte_test.go
+++ b/cvte_test.go
@@ -14,6 +14,8 @@ import (
 	"github.com/shockerli/cvt"
 )
 
+// [test data]
+
 // alias type: bool
 type AliasTypeBool bool
 
@@ -64,6 +66,10 @@ type TestStructC struct {
 	C1 string
 }
 
+func (c TestStructC) String() string {
+	return c.C1
+}
+
 type TestStructD struct {
 	D1 int
 }
@@ -73,6 +79,8 @@ type TestStructE struct {
 	DD *TestStructD
 }
 
+// [function tests]
+
 func TestBoolE(t *testing.T) {
 	tests := []struct {
 		input  interface{}
@@ -1389,3 +1397,44 @@ func TestSliceE(t *testing.T) {
 		assert.Equal(t, tt.expect, v, msg)
 	}
 }
+
+func TestFieldE(t *testing.T) {
+	tests := []struct {
+		input  interface{}
+		field  interface{}
+		expect interface{}
+		isErr  bool
+	}{
+		{TestStructE{D1: 1, DD: &TestStructD{D1: 2}}, "D1", 1, false},
+		{TestStructE{D1: 1, DD: &TestStructD{D1: 2}}, "DD", &TestStructD{D1: 2}, false},
+		{TestStructB{B1: 1, TestStructC: TestStructC{C1: "c1"}}, "C1", "c1", false},
+		{map[int]interface{}{123: "112233"}, "123", "112233", false},
+		{map[int]interface{}{123: "112233"}, 123, "112233", false},
+		{map[string]interface{}{"123": "112233"}, 123, "112233", false},
+		{map[string]interface{}{"c": "ccc"}, TestStructC{C1: "c"}, "ccc", false},
+
+		// errors
+		{TestStructE{D1: 1, DD: &TestStructD{D1: 2}}, "", nil, true},
+		{TestStructE{D1: 1, DD: &TestStructD{D1: 2}}, "Age", nil, true},
+		{int(123), "Name", nil, true},
+		{uint16(123), "Name", nil, true},
+		{float64(12.3), "Name", nil, true},
+		{func() {}, "Name", nil, true},
+	}
+
+	for i, tt := range tests {
+		msg := fmt.Sprintf(
+			"i = %d, input[%+v], field[%s], expect[%+v], isErr[%v]",
+			i, tt.input, tt.field, tt.expect, tt.isErr,
+		)
+
+		v, err := cvt.FieldE(tt.input, tt.field)
+		if tt.isErr {
+			assert.Error(t, err, msg)
+			continue
+		}
+
+		assert.NoError(t, err, msg)
+		assert.Equal(t, tt.expect, v, msg)
+	}
+}