Streamline type check in content constructs

category.go

@@ -8,19 +8,14 @@ import (
 
 type Category struct {
 	*CommonAttributes
-	Content Content `xml:"content"` // undefinedContent in RFC4287
-	Term    string  `xml:"term,attr"`
-	Scheme  IRI     `xml:"scheme,attr,omitempty"`
-	Label   string  `xml:"label,attr,omitempty"`
+	Content string `xml:",any"` // undefinedContent in RFC4287
+	Term    string `xml:"term,attr"`
+	Scheme  IRI    `xml:"scheme,attr,omitempty"`
+	Label   string `xml:"label,attr,omitempty"`
 }
 
 // NewCategory creates a new Category. It returns a *Category and an error.
-func NewCategory(term string) (*Category, error) {
-	content, err := NewContent(InlineText, "", "")
-	if err != nil {
-		return nil, fmt.Errorf("error creating content element: %v", err)
-	}
-
+func NewCategory(term, content string) (*Category, error) {
 	return &Category{Term: term, Content: content}, nil
 }
 
@@ -46,12 +41,8 @@ func (c *Category) Check() error {
 		return fmt.Errorf("label attribute %v of category not correctly escaped", c.Label)
 	}
 
-	if c.Content == nil {
-		return errors.New("no content element of category")
-	} else {
-		if err := c.Content.Check(); err != nil {
-			return fmt.Errorf("content element of category: %v", err)
-		}
+	if c.Content == "" {
+		return errors.New("content element of category empty")
 	}
 
 	return nil

inlineTextContent.go

@@ -3,7 +3,6 @@ package atom
 import (
 	"errors"
 	"fmt"
-	"reflect"
 )
 
 type InlineTextContent struct {
@@ -19,11 +18,12 @@ func newInlineTextContent(mediaType string, content any) (*InlineTextContent, er
 		return nil, fmt.Errorf("media type %v incompatible with inline text content", mediaType)
 	}
 
-	if reflect.TypeOf(content).Kind() != reflect.String {
+	text, ok := content.(string)
+	if !ok {
 		return nil, fmt.Errorf("content type %T incompatible with inline text content", content)
 	}
 
-	return &InlineTextContent{Type: mediaType, Text: content.(string)}, nil
+	return &InlineTextContent{Type: mediaType, Text: text}, nil
 }
 
 // isContent checks whether the InlineTextContent is a Content. It returns a

inlineXHTMLContent.go

@@ -3,13 +3,12 @@ package atom
 import (
 	"errors"
 	"fmt"
-	"reflect"
 )
 
 type InlineXHTMLContent struct {
 	*CommonAttributes
 	Type     string `xml:"type,attr"`
-	XHTMLDiv string `xml:"xhtmldiv"`
+	XHTMLDiv XHTMLDiv
 }
 
 // newInlineXHTMLContent creates a new InlineXHTMLContent. It returns a
@@ -19,11 +18,12 @@ func newInlineXHTMLContent(mediaType string, content any) (*InlineXHTMLContent,
 		return nil, fmt.Errorf("media type %v incompatible with inline xhtml content", mediaType)
 	}
 
-	if reflect.TypeOf(content).Kind() != reflect.String {
+	xhtmlDiv, ok := content.(XHTMLDiv)
+	if !ok {
 		return nil, fmt.Errorf("content type %T incompatible with inline xhtml content", content)
 	}
 
-	return &InlineXHTMLContent{Type: mediaType, XHTMLDiv: content.(string)}, nil
+	return &InlineXHTMLContent{Type: mediaType, XHTMLDiv: xhtmlDiv}, nil
 }
 
 // isContent checks whether the InlineXHTMLContent is a Content. It returns a
@@ -44,8 +44,8 @@ func (i *InlineXHTMLContent) Check() error {
 		return errors.New("type attribute of inline xhtml content must be xhtml")
 	}
 
-	if i.XHTMLDiv == "" {
-		return errors.New("xhtmlDiv element of inline xhtml content empty")
+	if err := i.XHTMLDiv.Check(); err != nil {
+		return fmt.Errorf("xhtml div element %v of inline xhtml content %v: %v", i.XHTMLDiv, i, err)
 	}
 
 	return nil

link.go

@@ -9,7 +9,7 @@ import (
 type Link struct {
 	*CommonAttributes
 	Title    string      `xml:"title,attr,omitempty"`
-	Content  Content     `xml:"content"` // undefinedContent in RFC4287
+	Content  string      `xml:",any"` // undefinedContent in RFC4287
 	Href     IRI         `xml:"href,attr"`
 	Rel      string      `xml:"rel,attr,omitempty"`
 	Type     MediaType   `xml:"type,attr,omitempty"`
@@ -18,12 +18,7 @@ type Link struct {
 }
 
 // NewLink creates a new Link. It returns a *Link and an error.
-func NewLink(href string) (*Link, error) {
-	content, err := NewContent(InlineText, "", "")
-	if err != nil {
-		return nil, fmt.Errorf("error creating content element: %v", err)
-	}
-
+func NewLink(href, content string) (*Link, error) {
 	return &Link{Href: IRI(href), Content: content}, nil
 }
 
@@ -56,12 +51,8 @@ func (l *Link) Check() error {
 		}
 	}
 
-	if l.Content == nil {
-		return fmt.Errorf("no content element of link %v", l.Href)
-	} else {
-		if err := l.Content.Check(); err != nil {
-			return fmt.Errorf("content element of link %v: %v", l.Href, err)
-		}
+	if l.Content == "" {
+		return errors.New("content element of link empty")
 	}
 
 	return nil

outOfLineContent.go

@@ -4,7 +4,6 @@ import (
 	"errors"
 	"fmt"
 	"mime"
-	"reflect"
 )
 
 type OutOfLineContent struct {
@@ -20,15 +19,16 @@ func newOutOfLineContent(mediaType string, content any) (*OutOfLineContent, erro
 		return nil, fmt.Errorf("media type %v incompatible with out of line content", mediaType)
 	}
 
-	if reflect.TypeOf(content).Kind() != reflect.String {
+	iri, ok := content.(IRI)
+	if !ok {
 		return nil, fmt.Errorf("content type %T incompatible with out of line content", content)
 	}
 
-	if !isValidIRI(content.(IRI)) {
+	if !isValidIRI(iri) {
 		return nil, errors.New("content not a valid uri")
 	}
 
-	return &OutOfLineContent{Type: MediaType(mediaType), SRC: content.(IRI)}, nil
+	return &OutOfLineContent{Type: MediaType(mediaType), SRC: iri}, nil
 }
 
 // isContent checks whether the OutOfLineContent is a Content. It returns a

xhtmlDiv.go

@@ -0,0 +1,30 @@
+package atom
+
+import (
+	"encoding/xml"
+	"errors"
+)
+
+type XHTMLDiv struct {
+	XMLName xml.Name `xml:"div"`
+	XMLNS   string   `xml:"xmlns,attr"`
+	Content string   `xml:",innerxml"`
+}
+
+// NewXHTMLDiv creates a new XHTMLDiv. It returns a *XHTMLDiv.
+func NewXHTMLDiv(content string) *XHTMLDiv {
+	return &XHTMLDiv{
+		XMLNS:   "http://www.w3.org/1999/xhtml",
+		Content: content,
+	}
+}
+
+// Check checks the XHTMLDiv for incompatibilities with RFC4287. It returns an
+// error.
+func (x *XHTMLDiv) Check() error {
+	if x.XMLNS != "http://www.w3.org/1999/xhtml" {
+		return errors.New("xmlns attribute of xhtml text must be http://www.w3.org/1999/xhtml")
+	}
+
+	return nil
+}

xhtmlText.go

@@ -1,16 +1,10 @@
 package atom
 
 import (
-	"encoding/xml"
 	"errors"
+	"fmt"
 )
 
-type XHTMLDiv struct {
-	XMLName xml.Name `xml:"div"`
-	XMLNS   string   `xml:"xmlns,attr"`
-	Content string   `xml:",innerxml"`
-}
-
 type XHTMLText struct {
 	*CommonAttributes
 	Type     string `xml:"type,attr"` // Must be xhtml
@@ -27,8 +21,8 @@ func (x *XHTMLText) Check() error {
 		return errors.New("type attribute of xhtml text must be xhtml")
 	}
 
-	if x.XHTMLDiv.XMLNS != "http://www.w3.org/1999/xhtml" {
-		return errors.New("xmlns attribute of xhtml text must be http://www.w3.org/1999/xhtml")
+	if err := x.XHTMLDiv.Check(); err != nil {
+		return fmt.Errorf("xhtml div element %v of xhtml text %v: %v", x.XHTMLDiv, x, err)
 	}
 
 	return nil