SelectedColumns (#6)

* fix: README.md

* feat: rename

* tmp

* feat: add test of selectedColumns

* feat: add SelectedColumns

README.md

@@ -8,9 +8,6 @@ Most of the programs related to csv generation and reading are created from code
  
 ※xsv does not include gocsv.
 
-## 🚧Under Construction
-there is a lot of things to do before release.
-
 ## Getting Started
 
 ```

encode_test.go

@@ -607,3 +607,36 @@ func Test_writeTo_nested_struct(t *testing.T) {
 	assertLine(t, []string{"one.boolField1", "one.stringField2", "two.boolField1", "two.stringField2", "three.boolField1", "three.stringField2"}, lines[0])
 	assertLine(t, []string{"false", "email_one", "true", "email_two", "false", "email_three"}, lines[1])
 }
+
+func Test_writeTo_emptyptr_selectedColumns(t *testing.T) {
+
+	b := bytes.Buffer{}
+	e := &encoder{out: &b}
+	blah := 2
+	sptr := "*string"
+	s := []EmbedPtrSample{
+		{
+			Qux:    "aaa",
+			Sample: &Sample{Foo: "f", Bar: 1, Baz: "baz", Frop: 0.2, Blah: &blah, SPtr: &sptr},
+			Ignore: "shouldn't be marshalled",
+			Quux:   "zzz",
+			Grault: math.Pi,
+		},
+	}
+
+	xsvWrite := NewXsvWrite[EmbedPtrSample]()
+	xsvWrite.SelectedColumns = []string{"first", "-", "Baz", "last"} //　If a "-" exists here, it will not be output.
+	if err := xsvWrite.SetWriter(csv.NewWriter(e.out)).Write(s); err != nil {
+		t.Fatal(err)
+	}
+
+	lines, err := csv.NewReader(&b).ReadAll()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(lines) != 2 {
+		t.Fatalf("expected 2 lines, got %d", len(lines))
+	}
+	assertLine(t, []string{"first", "Baz", "last"}, lines[0])
+	assertLine(t, []string{"aaa", "baz", "zzz"}, lines[1])
+}

xsv_write.go

@@ -4,31 +4,45 @@ import (
 	"bytes"
 	"encoding/csv"
 	"os"
+	"slices"
 )
 
 type XsvWrite[T any] struct {
-	TagName             string //key in the struct field's tag to scan
-	TagSeparator        string //separator string for multiple csv tags in struct fields
-	OmitHeaders         bool
-	selectedColumnIndex []int        // TODO: describe in comment
-	columnSorter        ColumnSorter // TODO: describe in comment
-	nameNormalizer      Normalizer
+	TagName         string //key in the struct field's tag to scan
+	TagSeparator    string //separator string for multiple csv tags in struct fields
+	OmitHeaders     bool
+	SelectedColumns []string     // slice of field names to output
+	columnSorter    ColumnSorter // TODO: describe in comment
+	nameNormalizer  Normalizer
 }
+type ColumnSorter = func(row []string) []string
 
 func NewXsvWrite[T any]() XsvWrite[T] {
 	return XsvWrite[T]{
-		TagName:             "csv",
-		TagSeparator:        ",",
-		OmitHeaders:         false,
-		selectedColumnIndex: make([]int, 0),
+		TagName:         "csv",
+		TagSeparator:    ",",
+		OmitHeaders:     false,
+		SelectedColumns: make([]string, 0),
 		columnSorter: func(row []string) []string {
 			return row
 		},
 		nameNormalizer: func(s string) string { return s },
 	}
 }
 
-type ColumnSorter = func(row []string) []string
+func (x *XsvWrite[T]) getSelectedFieldInfos(fieldInfos []fieldInfo) []fieldInfo {
+	if len(x.SelectedColumns) > 0 {
+		var selectedFieldInfos []fieldInfo
+		for _, info := range fieldInfos {
+			if slices.Index(x.SelectedColumns, info.keys[0]) >= 0 {
+				selectedFieldInfos = append(selectedFieldInfos, info)
+			}
+		}
+		return selectedFieldInfos
+	} else {
+		return fieldInfos
+	}
+}
 
 func (x *XsvWrite[T]) SetWriter(writer *csv.Writer) (xw *XsvWriter[T]) {
 	xw = NewXsvWriter(*x)

xsv_writer.go

@@ -33,10 +33,9 @@ func (xw *XsvWriter[T]) Write(data []T) error {
 	}
 
 	fieldInfos := getFieldInfos(inInnerType, []int{}, []string{}, xw.TagName, xw.TagSeparator, xw.nameNormalizer) // Get the inner struct info to get CSV annotations
+	fieldInfos = xw.getSelectedFieldInfos(fieldInfos)
 	inInnerStructInfo := &structInfo{fieldInfos}
 
-	inInnerStructInfo.Fields = getPickedFields(inInnerStructInfo.Fields, xw.selectedColumnIndex) // Filter Fields from all fields
-
 	csvHeadersLabels := make([]string, len(inInnerStructInfo.Fields))
 	for i, fieldInfo := range inInnerStructInfo.Fields { // Used to write the header (first line) in CSV
 		csvHeadersLabels[i] = fieldInfo.getFirstKey()
@@ -78,8 +77,8 @@ func (xw *XsvWriter[T]) WriteFromChan(dataChan chan T) error {
 	}
 	inInnerWasPointer := inType.Kind() == reflect.Ptr
 	fieldInfos := getFieldInfos(inType, []int{}, []string{}, xw.TagName, xw.TagSeparator, xw.nameNormalizer) // Get the inner struct info to get CSV annotations
+	fieldInfos = xw.getSelectedFieldInfos(fieldInfos)
 	inInnerStructInfo := &structInfo{fieldInfos}
-	inInnerStructInfo.Fields = getPickedFields(inInnerStructInfo.Fields, xw.selectedColumnIndex) // Filtered out ignoreFields from all fields
 	csvHeadersLabels := make([]string, len(inInnerStructInfo.Fields))
 	for i, fieldInfo := range inInnerStructInfo.Fields { // Used to Write the header (first line) in CSV
 		csvHeadersLabels[i] = fieldInfo.getFirstKey()