Make NewCommonAttributes public

README.md

@@ -2,7 +2,7 @@
 
 An extensible Atom feed generator library that aims to be very close to RFC4287.
 It diligently checks for compliance with the standard and provides functions for
-easy creation and extension of elements.
+easy creation, extension and deletion of elements.
 
 ## Installation
 
@@ -14,45 +14,47 @@ go get git.streifling.com/jason/atom@latest
 
 ## Usage
 
-This library provides convenient functions to safely create and extend elements
+### Basic Feed
-and attributes of Atom feeds. It also provides checks for all constructs'
+
-adherence to RFC4287.
+This library provides convenient functions to safely create, extend and delete
+elements and attributes of Atom feeds. It also provides checks for all
+constructs' adherence to RFC4287.
 
 ```go
 package main
 
 import (
- "fmt"
+    "fmt"
- "log"
+    "log"
 
- "git.streifling.com/jason/atom"
+    "git.streifling.com/jason/atom"
 )
 
 func main() {
- feed := atom.NewFeed("Example Feed")
+    feed := atom.NewFeed("Example Feed")
- if err := feed.Check(); err != nil {
+    if err := feed.Check(); err != nil {
-  log.Fatalln(err)
+        log.Fatalln(err)
- }
+    }
 
- author := atom.NewPerson("John Doe")
+    author := atom.NewPerson("John Doe")
- author.Email = "john.doe@example.com"
+    author.Email = "john.doe@example.com"
- if err := author.Check(); err != nil {
+    if err := author.Check(); err != nil {
-  log.Fatalln(err)
+        log.Fatalln(err)
- }
+    }
- feed.AddAuthor(author)
+    feed.AddAuthor(author)
 
- entry := atom.NewEntry("First Entry")
+    entry := atom.NewEntry("First Entry")
- entry.Content = atom.NewContent(atom.InlineText, "text", "This is the content of the first entry.")
+    entry.Content = atom.NewContent(atom.InlineText, "text", "This is the content of the first entry.")
- if err := entry.Check(); err != nil {
+    if err := entry.Check(); err != nil {
-  log.Fatalln(err)
+        log.Fatalln(err)
- }
+    }
- feed.AddEntry(entry)
+    feed.AddEntry(entry)
 
- feedString, err := feed.ToXML("utf-8")
+    feedString, err := feed.ToXML("UTF-8")
- if err != nil {
+    if err != nil {
-  log.Fatalln(err)
+        log.Fatalln(err)
- }
+    }
- fmt.Println(feedString)
+    fmt.Println(feedString)
 }
 ```
 
@@ -63,70 +65,177 @@ provide.
 package main
 
 import (
- "fmt"
+    "fmt"
- "log"
+    "log"
- "time"
+    "time"
 
- "git.streifling.com/jason/atom"
+    "git.streifling.com/jason/atom"
+    "github.com/google/uuid"
 )
 
 func main() {
- now := time.Now()
+    now := time.Now()
 
- feed := &atom.Feed{
+    feed := &atom.Feed{
-  Title: &atom.PlainText{
+        Title: &atom.PlainText{
-   Type: "text",
+            Type: "text",
-   Text: "Example Feed",
+            Text: "Example Feed",
-  },
+        },
-  ID:      &atom.ID{URI: "urn:uuid:60a76c80-d399-11d9-b93C-0003939e0af6"},
+        ID:      &atom.ID{URI: fmt.Sprint("urn:uuid:", uuid.New())},
-  Updated: &atom.Date{DateTime: atom.DateTime(now)},
+        Updated: &atom.Date{DateTime: atom.DateTime(now)},
-  Authors: []*atom.Person{
+        Authors: []*atom.Person{
-   {
+            {
-    Name:  "John Doe",
+                Name:  "John Doe",
-    Email: "john.doe@example.com",
+                Email: "john.doe@example.com",
-   },
+            },
-  },
+        },
-  Entries: []*atom.Entry{
+        Entries: []*atom.Entry{
-   {
+            {
-    Title: &atom.PlainText{
+                Title: &atom.PlainText{
-     Type: "text",
+                    Type: "text",
-     Text: "First Entry",
+                    Text: "First Entry",
-    },
+                },
-    ID:      &atom.ID{URI: "urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efa6a"},
+                ID:      &atom.ID{URI: fmt.Sprint("urn:uuid:", uuid.New())},
-    Updated: &atom.Date{DateTime: atom.DateTime(now)},
+                Updated: &atom.Date{DateTime: atom.DateTime(now)},
-    Content: &atom.InlineTextContent{
+                Content: &atom.InlineTextContent{
-     Type: "text",
+                    Type: "text",
-     Text: "This is the content of the first entry.",
+                    Text: "This is the content of the first entry.",
-    },
+                },
-   },
+            },
-  },
+        },
- }
+    }
 
- feedString, err := feed.ToXML("utf-8")
+    feedString, err := feed.ToXML("UTF-8")
- if err != nil {
+    if err != nil {
-  log.Fatalln(err)
+        log.Fatalln(err)
- }
+    }
- fmt.Println(feedString)
+    fmt.Println(feedString)
 }
 ```
 
 The output of both ways of using it is an RFC4287 compliant Atom feed.
 
 ```xml
-<?xml version="1.0" encoding="utf-8"?>
+<?xml version="1.0" encoding="UTF-8"?>
 <feed xmlns="http://www.w3.org/2005/Atom">
-  <author>
+    <author>
-    <name>John Doe</name>
+        <name>John Doe</name>
-    <email>john.doe@example.com</email>
+        <email>john.doe@example.com</email>
-  </author>
+    </author>
-  <id>urn:uuid:60a76c80-d399-11d9-b93C-0003939e0af6</id>
+    <id>urn:uuid:60a76c80-d399-11d9-b93C-0003939e0af6</id>
-  <title type="text">Example Feed</title>
+    <title type="text">Example Feed</title>
-  <updated>2024-10-18T05:49:08+02:00</updated>
+    <updated>2024-10-18T05:49:08+02:00</updated>
-  <entry>
+    <entry>
-    <content type="text">This is the content of the first entry.</content>
+        <content type="text">This is the content of the first entry.</content>
-    <id>urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efa6a</id>
+        <id>urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efa6a</id>
-    <title type="text">First Entry</title>
+        <title type="text">First Entry</title>
-    <updated>2006-01-02T15:04:05+07:00</updated>
+        <updated>2006-01-02T15:04:05+07:00</updated>
-  </entry>
+    </entry>
+</feed>
+```
+
+### Compliance and Error Checking
+
+All Atom constructs have their own ```construct.Check()``` method. It checks for
+compliance with RFC4287 and errors. This allows one to be certain that only
+compliant constructs are added to their respective parent construct. It also
+means that not the entire feed has to be checked every time a new construct is
+added. Instead one only checks the current construct and all of its
+sub-constructs with a single ```construct.Check()``` call.
+
+```go
+package main
+
+import (
+    "fmt"
+    "log"
+
+    "git.streifling.com/jason/atom"
+)
+
+func main() {
+    feed := atom.NewFeed("Example Feed")
+    if err := feed.Check(); err != nil {
+        log.Fatalln(err)
+    }
+
+    entry := atom.NewEntry("One")
+    entry.Content = atom.NewContent(atom.InlineText, "text", "Entry One")
+    entry.AddAuthor(atom.NewPerson("John Doe"))
+    if err := entry.Check(); err != nil {
+        log.Fatalln(err)
+    }
+    feed.AddEntry(entry)
+
+    feedString, err := feed.ToXML("UTF-8")
+    if err != nil {
+        log.Fatalln(err)
+    }
+    fmt.Println(feedString)
+}
+```
+
+### Adding and Deleting Items
+
+To add elements to any slice one calls the appropriate
+```someone.AddSomething(toBeAdded)``` method. It returns the item's index
+number. To delete the item one calls the Delete method.
+
+```go
+package main
+
+import (
+    "fmt"
+    "log"
+
+    "git.streifling.com/jason/atom"
+)
+
+func main() {
+    feed := atom.NewFeed("Feed")
+    if err := feed.Check(); err != nil {
+        log.Fatalln(err)
+    }
+
+    e1 := atom.NewEntry("One")
+    e1.Content = atom.NewContent(atom.InlineText, "text", "Entry One")
+    if err := e1.Check(); err != nil {
+        log.Fatalln(err)
+    }
+    i1 := feed.AddEntry(e1)
+
+    e2 := atom.NewEntry("Two")
+    e2.Content = atom.NewContent(atom.InlineText, "text", "Entry Two")
+    if err := e2.Check(); err != nil {
+        log.Fatalln(err)
+    }
+    feed.AddEntry(e2)
+
+    if err := feed.DeleteEntry(i1); err != nil {
+        log.Fatalln(err)
+    }
+
+    feedString, err := feed.ToXML("UTF-8")
+    if err != nil {
+        log.Fatalln(err)
+    }
+    fmt.Println(feedString)
+}
+```
+
+The output of this example looks like this. It only shows the second entry.
+
+```xml
+<?xml version="1.0" encoding="UTF-8"?>
+<feed xmlns="http://www.w3.org/2005/Atom">
+    <id>urn:uuid:ae89d343-b535-447d-ac14-4b80d3e02a2f</id>
+    <title type="text">Example Feed</title>
+    <updated>2024-10-20T14:57:02+02:00</updated>
+    <entry>
+        <content type="text">Entry Two</content>
+        <id>urn:uuid:620c6f73-ee1d-4c1e-be98-b0b1ad7a053f</id>
+        <title type="text">Two</title>
+        <updated>2024-10-20T14:57:02+02:00</updated>
+    </entry>
 </feed>
 ```

atom.go

@@ -16,12 +16,14 @@ type Countable interface {
 	*xml.Attr | *Person | *Category | *Link | *ExtensionElement | *Entry
 }
 
-// addToSlice adds a Countable to to a *[]Countable
+// addToSlice adds a Countable to to a *[]Countable. It returns an int.
-func addToSlice[C Countable](slice *[]C, countable C) {
+func addToSlice[C Countable](slice *[]C, countable C) int {
 	if *slice == nil {
 		*slice = make([]C, 0)
 	}
+
 	*slice = append(*slice, countable)
+	return len(*slice) - 1
 }
 
 // deleteFromSlice deletes the Countable with the index from the *[]Countable.

category.go

@@ -10,22 +10,17 @@ type Category struct {
 	*CommonAttributes
 	Term   string `xml:"term,attr"`
 	Scheme string `xml:"scheme,attr,omitempty"` // IRI
-	Label  string `xml:"label,attr,omitempty"`
+	Label  string `xml:"label,attr,omitempty"`  // Must be unescaped
 }
 
 // NewCategory creates a new Category. It returns a *Category.
 func NewCategory(term string) *Category {
 	return &Category{
-		CommonAttributes: newCommonAttributes(),
+		CommonAttributes: NewCommonAttributes(),
 		Term:             term,
 	}
 }
 
-// SetLabel sets the Label attribute of the Category.
-func (c *Category) SetLabel(label string) {
-	c.Label = Unescape(label)
-}
-
 // Check checks the Category for incompatibilities with RFC4287. It returns an
 // error.
 func (c *Category) Check() error {

commonAttributes.go

@@ -13,13 +13,14 @@ type CommonAttributes struct {
 
 // NewCommonAttributes creates a new set of CommonAttributes. It returns a
 // *CommonAttributes.
-func newCommonAttributes() *CommonAttributes {
+func NewCommonAttributes() *CommonAttributes {
 	return new(CommonAttributes)
 }
 
-// AddAttribute adds the attribute to the CommonAttributes.
+// AddAttribute adds the attribute to the CommonAttributes. It returns its index
-func (c *CommonAttributes) AddAttribute(name, value string) {
+// as an int.
-	addToSlice(&c.UndefinedAttributes, &xml.Attr{Name: xml.Name{Local: name}, Value: value})
+func (c *CommonAttributes) AddAttribute(name, value string) int {
+	return addToSlice(&c.UndefinedAttributes, &xml.Attr{Name: xml.Name{Local: name}, Value: value})
 }
 
 // DeleteAttribute deletes the attribute at index from the CommonAttributes. It

date.go

@@ -19,7 +19,7 @@ func DateTime(t time.Time) string {
 // NewDate creates a new Date. It returns a *Date.
 func NewDate(t time.Time) *Date {
 	return &Date{
-		CommonAttributes: newCommonAttributes(),
+		CommonAttributes: NewCommonAttributes(),
 		DateTime:         DateTime(t),
 	}
 }

entry.go

@@ -59,17 +59,23 @@ func (e *Entry) checkAuthors(authorInFeed bool) error {
 // NewEntry creates a new Entry. It returns a *Entry.
 func NewEntry(title string) *Entry {
 	return &Entry{
-		CommonAttributes: newCommonAttributes(),
+		CommonAttributes: NewCommonAttributes(),
 		ID:               NewID(NewURN()),
 		Title:            NewText("text", title),
 		Updated:          NewDate(time.Now()),
 	}
 }
 
-// AddAuthor adds the Person as an author to the Entry.
+// AddAuthor adds the Person as an author to the Entry. It returns its index as
-func (e *Entry) AddAuthor(p *Person) {
+// an int.
-	addToSlice(&e.Authors, p)
+func (e *Entry) AddAuthor(p *Person) int {
-	e.Updated = NewDate(time.Now())
+	if e.Updated == nil {
+		e.Updated = NewDate(time.Now())
+	} else {
+		e.Updated.DateTime = DateTime(time.Now())
+	}
+
+	return addToSlice(&e.Authors, p)
 }
 
 // DeleteAuthor deletes the Person at index from the Entry. It return an error.
@@ -78,14 +84,24 @@ func (e *Entry) DeleteAuthor(index int) error {
 		return fmt.Errorf("error deleting author %v from entry %v: %v", index, e.ID.URI, err)
 	}
 
-	e.Updated = NewDate(time.Now())
+	if e.Updated == nil {
+		e.Updated = NewDate(time.Now())
+	} else {
+		e.Updated.DateTime = DateTime(time.Now())
+	}
+
 	return nil
 }
 
-// AddCategory adds the Category to the Entry.
+// AddCategory adds the Category to the Entry. It returns ts index as an int.
-func (e *Entry) AddCategory(c *Category) {
+func (e *Entry) AddCategory(c *Category) int {
-	addToSlice(&e.Categories, c)
+	if e.Updated == nil {
-	e.Updated = NewDate(time.Now())
+		e.Updated = NewDate(time.Now())
+	} else {
+		e.Updated.DateTime = DateTime(time.Now())
+	}
+
+	return addToSlice(&e.Categories, c)
 }
 
 // DeleteCategory deletes the Category at index from the Entry. It return an
@@ -95,14 +111,25 @@ func (e *Entry) DeleteCategory(index int) error {
 		return fmt.Errorf("error deleting category %v from entry %v: %v", index, e.ID.URI, err)
 	}
 
-	e.Updated = NewDate(time.Now())
+	if e.Updated == nil {
+		e.Updated = NewDate(time.Now())
+	} else {
+		e.Updated.DateTime = DateTime(time.Now())
+	}
+
 	return nil
 }
 
-// AddContributor adds the Person as a contributor to the Entry.
+// AddContributor adds the Person as a contributor to the Entry. It returns its
-func (e *Entry) AddContributor(c *Person) {
+// index as an int.
-	addToSlice(&e.Contributors, c)
+func (e *Entry) AddContributor(c *Person) int {
-	e.Updated = NewDate(time.Now())
+	if e.Updated == nil {
+		e.Updated = NewDate(time.Now())
+	} else {
+		e.Updated.DateTime = DateTime(time.Now())
+	}
+
+	return addToSlice(&e.Contributors, c)
 }
 
 // DeleteContributor deletes the Person at index from the Entry. It return an
@@ -112,14 +139,24 @@ func (e *Entry) DeleteContributor(index int) error {
 		return fmt.Errorf("error deleting contributor %v from entry %v: %v", index, e.ID.URI, err)
 	}
 
-	e.Updated = NewDate(time.Now())
+	if e.Updated == nil {
+		e.Updated = NewDate(time.Now())
+	} else {
+		e.Updated.DateTime = DateTime(time.Now())
+	}
+
 	return nil
 }
 
-// AddLink adds the Link to the Entry.
+// AddLink adds the Link to the Entry. It returns its index as an int.
-func (e *Entry) AddLink(l *Link) {
+func (e *Entry) AddLink(l *Link) int {
-	addToSlice(&e.Links, l)
+	if e.Updated == nil {
-	e.Updated = NewDate(time.Now())
+		e.Updated = NewDate(time.Now())
+	} else {
+		e.Updated.DateTime = DateTime(time.Now())
+	}
+
+	return addToSlice(&e.Links, l)
 }
 
 // DeleteLink deletes the Link at index from the Entry. It return an error.
@@ -128,14 +165,25 @@ func (e *Entry) DeleteLink(index int) error {
 		return fmt.Errorf("error deleting link %v from entry %v: %v", index, e.ID.URI, err)
 	}
 
-	e.Updated = NewDate(time.Now())
+	if e.Updated == nil {
+		e.Updated = NewDate(time.Now())
+	} else {
+		e.Updated.DateTime = DateTime(time.Now())
+	}
+
 	return nil
 }
 
-// AddExtension adds the ExtensionElement to the Entry.
+// AddExtension adds the ExtensionElement to the Entry. It returns its index as
-func (e *Entry) AddExtension(x *ExtensionElement) {
+// an int.
-	addToSlice(&e.Extensions, x)
+func (e *Entry) AddExtension(x *ExtensionElement) int {
-	e.Updated = NewDate(time.Now())
+	if e.Updated == nil {
+		e.Updated = NewDate(time.Now())
+	} else {
+		e.Updated.DateTime = DateTime(time.Now())
+	}
+
+	return addToSlice(&e.Extensions, x)
 }
 
 // DeleteExtension deletes the Extension at index from the Entry. It return an
@@ -145,7 +193,12 @@ func (e *Entry) DeleteExtension(index int) error {
 		return fmt.Errorf("error deleting extension %v from entry %v: %v", index, e.ID.URI, err)
 	}
 
-	e.Updated = NewDate(time.Now())
+	if e.Updated == nil {
+		e.Updated = NewDate(time.Now())
+	} else {
+		e.Updated.DateTime = DateTime(time.Now())
+	}
+
 	return nil
 }
 

feed.go

@@ -28,17 +28,23 @@ type Feed struct {
 // NewFeed creates a new Feed. It returns a *Feed.
 func NewFeed(title string) *Feed {
 	return &Feed{
-		CommonAttributes: newCommonAttributes(),
+		CommonAttributes: NewCommonAttributes(),
 		ID:               NewID(NewURN()),
 		Title:            NewText("text", title),
 		Updated:          NewDate(time.Now()),
 	}
 }
 
-// AddAuthor adds the Person as an author to the Feed.
+// AddAuthor adds the Person as an author to the Feed. It returns its index as
-func (f *Feed) AddAuthor(p *Person) {
+// an int.
-	addToSlice(&f.Authors, p)
+func (f *Feed) AddAuthor(p *Person) int {
-	f.Updated = NewDate(time.Now())
+	if f.Updated == nil {
+		f.Updated = NewDate(time.Now())
+	} else {
+		f.Updated.DateTime = DateTime(time.Now())
+	}
+
+	return addToSlice(&f.Authors, p)
 }
 
 // DeleteAuthor deletes the Person at index from the Feed. It return an error.
@@ -47,14 +53,24 @@ func (f *Feed) DeleteAuthor(index int) error {
 		return fmt.Errorf("error deleting author %v from entry %v: %v", index, f.ID.URI, err)
 	}
 
-	f.Updated = NewDate(time.Now())
+	if f.Updated == nil {
+		f.Updated = NewDate(time.Now())
+	} else {
+		f.Updated.DateTime = DateTime(time.Now())
+	}
+
 	return nil
 }
 
-// AddCategory adds the Category to the Feed.
+// AddCategory adds the Category to the Feed. It returns its index as an int.
-func (f *Feed) AddCategory(c *Category) {
+func (f *Feed) AddCategory(c *Category) int {
-	addToSlice(&f.Categories, c)
+	if f.Updated == nil {
-	f.Updated = NewDate(time.Now())
+		f.Updated = NewDate(time.Now())
+	} else {
+		f.Updated.DateTime = DateTime(time.Now())
+	}
+
+	return addToSlice(&f.Categories, c)
 }
 
 // DeleteCategory deletes the Category at index from the Feed. It return an
@@ -64,14 +80,25 @@ func (f *Feed) DeleteCategory(index int) error {
 		return fmt.Errorf("error deleting category %v from entry %v: %v", index, f.ID.URI, err)
 	}
 
-	f.Updated = NewDate(time.Now())
+	if f.Updated == nil {
+		f.Updated = NewDate(time.Now())
+	} else {
+		f.Updated.DateTime = DateTime(time.Now())
+	}
+
 	return nil
 }
 
-// AddContributor adds the Person as a contributor to the Feed.
+// AddContributor adds the Person as a contributor to the Feed. It returns its
-func (f *Feed) AddContributor(c *Person) {
+// index as an int.
-	addToSlice(&f.Contributors, c)
+func (f *Feed) AddContributor(c *Person) int {
-	f.Updated = NewDate(time.Now())
+	if f.Updated == nil {
+		f.Updated = NewDate(time.Now())
+	} else {
+		f.Updated.DateTime = DateTime(time.Now())
+	}
+
+	return addToSlice(&f.Contributors, c)
 }
 
 // DeleteContributor deletes the Person at index from the Feed. It return an
@@ -81,14 +108,25 @@ func (f *Feed) DeleteContributor(index int) error {
 		return fmt.Errorf("error deleting contributor %v from entry %v: %v", index, f.ID.URI, err)
 	}
 
-	f.Updated = NewDate(time.Now())
+	if f.Updated == nil {
+		f.Updated = NewDate(time.Now())
+	} else {
+		f.Updated.DateTime = DateTime(time.Now())
+	}
+
 	return nil
 }
 
 // AddLink adds the Link to the Feed. There should be one Link with Rel "self".
-func (f *Feed) AddLink(l *Link) {
+// It returns its index as an int.
-	addToSlice(&f.Links, l)
+func (f *Feed) AddLink(l *Link) int {
-	f.Updated = NewDate(time.Now())
+	if f.Updated == nil {
+		f.Updated = NewDate(time.Now())
+	} else {
+		f.Updated.DateTime = DateTime(time.Now())
+	}
+
+	return addToSlice(&f.Links, l)
 }
 
 // DeleteLink deletes the Link at index from the Feed. It return an error.
@@ -97,14 +135,24 @@ func (f *Feed) DeleteLink(index int) error {
 		return fmt.Errorf("error deleting link %v from entry %v: %v", index, f.ID.URI, err)
 	}
 
-	f.Updated = NewDate(time.Now())
+	if f.Updated == nil {
+		f.Updated = NewDate(time.Now())
+	} else {
+		f.Updated.DateTime = DateTime(time.Now())
+	}
+
 	return nil
 }
 
-// AddExtension adds the Extension to the Feed.
+// AddExtension adds the Extension to the Feed. It returns its index as an int.
-func (f *Feed) AddExtension(e *ExtensionElement) {
+func (f *Feed) AddExtension(e *ExtensionElement) int {
-	addToSlice(&f.Extensions, e)
+	if f.Updated == nil {
-	f.Updated = NewDate(time.Now())
+		f.Updated = NewDate(time.Now())
+	} else {
+		f.Updated.DateTime = DateTime(time.Now())
+	}
+
+	return addToSlice(&f.Extensions, e)
 }
 
 // DeleteExtension deletes the Extension at index from the Feed. It return an
@@ -114,14 +162,24 @@ func (f *Feed) DeleteExtension(index int) error {
 		return fmt.Errorf("error deleting extension %v from entry %v: %v", index, f.ID.URI, err)
 	}
 
-	f.Updated = NewDate(time.Now())
+	if f.Updated == nil {
+		f.Updated = NewDate(time.Now())
+	} else {
+		f.Updated.DateTime = DateTime(time.Now())
+	}
+
 	return nil
 }
 
-// AddEntry adds the Entry to the Feed.
+// AddEntry adds the Entry to the Feed. It returns its index as an int.
-func (f *Feed) AddEntry(e *Entry) {
+func (f *Feed) AddEntry(e *Entry) int {
-	addToSlice(&f.Entries, e)
+	if f.Updated == nil {
-	f.Updated = NewDate(time.Now())
+		f.Updated = NewDate(time.Now())
+	} else {
+		f.Updated.DateTime = DateTime(time.Now())
+	}
+
+	return addToSlice(&f.Entries, e)
 }
 
 // DeleteEntry deletes the Entry at index from the Feed. It return an error.
@@ -130,7 +188,12 @@ func (f *Feed) DeleteEntry(index int) error {
 		return fmt.Errorf("error deleting entry %v from entry %v: %v", index, f.ID.URI, err)
 	}
 
-	f.Updated = NewDate(time.Now())
+	if f.Updated == nil {
+		f.Updated = NewDate(time.Now())
+	} else {
+		f.Updated.DateTime = DateTime(time.Now())
+	}
+
 	return nil
 }
 
@@ -152,7 +215,12 @@ func (f *Feed) DeleteEntryByURI(uri string) error {
 	}
 
 	f.Entries = append(f.Entries[:index], f.Entries[index+1:]...)
-	f.Updated = NewDate(time.Now())
+	if f.Updated == nil {
+		f.Updated = NewDate(time.Now())
+	} else {
+		f.Updated.DateTime = DateTime(time.Now())
+	}
+
 	return nil
 }
 

generator.go

@@ -17,7 +17,7 @@ type Generator struct {
 // NewGenerator creates a new Generator. It returns a *Generator.
 func NewGenerator(text string) *Generator {
 	return &Generator{
-		CommonAttributes: newCommonAttributes(),
+		CommonAttributes: NewCommonAttributes(),
 		Text:             html.UnescapeString(text),
 	}
 }

icon.go

@@ -15,7 +15,7 @@ type Icon struct {
 // NewIcon creates a new Icon. It returns a *Icon.
 func NewIcon(uri string) *Icon {
 	return &Icon{
-		CommonAttributes: newCommonAttributes(),
+		CommonAttributes: NewCommonAttributes(),
 		URI:              uri,
 	}
 }

id.go

@@ -15,7 +15,7 @@ type ID struct {
 // NewID creates a new ID. It returns a *ID.
 func NewID(uri string) *ID {
 	return &ID{
-		CommonAttributes: newCommonAttributes(),
+		CommonAttributes: NewCommonAttributes(),
 		URI:              uri,
 	}
 }

inlineOtherContent.go

@@ -19,7 +19,7 @@ func newInlineOtherContent(mediaType string, content any) *InlineOtherContent {
 	mediaType, _, _ = mime.ParseMediaType(mediaType)
 
 	return &InlineOtherContent{
-		CommonAttributes: newCommonAttributes(),
+		CommonAttributes: NewCommonAttributes(),
 		Type:             mediaType,
 		AnyElement:       content,
 	}

inlineTextContent.go

@@ -16,7 +16,7 @@ type InlineTextContent struct {
 // *InlineTextContent.
 func newInlineTextContent(mediaType, text string) *InlineTextContent {
 	return &InlineTextContent{
-		CommonAttributes: newCommonAttributes(),
+		CommonAttributes: NewCommonAttributes(),
 		Type:             mediaType,
 		Text:             text,
 	}

inlineXHTMLContent.go

@@ -16,7 +16,7 @@ type InlineXHTMLContent struct {
 // *InlineXHTMLContent.
 func newInlineXHTMLContent(mediaType string, div *XHTMLDiv) *InlineXHTMLContent {
 	return &InlineXHTMLContent{
-		CommonAttributes: newCommonAttributes(),
+		CommonAttributes: NewCommonAttributes(),
 		Type:             mediaType,
 		XHTMLDiv:         div,
 	}

link.go

@@ -20,7 +20,7 @@ type Link struct {
 // NewLink creates a new Link. It returns a *Link.
 func NewLink(href string) *Link {
 	return &Link{
-		CommonAttributes: newCommonAttributes(),
+		CommonAttributes: NewCommonAttributes(),
 		Href:             href,
 	}
 }

logo.go

@@ -14,7 +14,7 @@ type Logo struct {
 // NewLogo creates a new Logo. It returns a *Logo.
 func NewLogo(uri string) *Logo {
 	return &Logo{
-		CommonAttributes: newCommonAttributes(),
+		CommonAttributes: NewCommonAttributes(),
 		URI:              uri,
 	}
 }

outOfLineContent.go

@@ -19,7 +19,7 @@ func newOutOfLineContent(mediaType, src string) *OutOfLineContent {
 	mediaType, _, _ = mime.ParseMediaType(mediaType)
 
 	return &OutOfLineContent{
-		CommonAttributes: newCommonAttributes(),
+		CommonAttributes: NewCommonAttributes(),
 		Type:             mediaType,
 		SRC:              src,
 	}

person.go

@@ -16,14 +16,15 @@ type Person struct {
 // NewPerson creates a new Person. It returns a *Person.
 func NewPerson(name string) *Person {
 	return &Person{
-		CommonAttributes: newCommonAttributes(),
+		CommonAttributes: NewCommonAttributes(),
 		Name:             name,
 	}
 }
 
-// AddExtension adds the Extension to the Person.
+// AddExtension adds the Extension to the Person. It returns its index as an
-func (p *Person) AddExtension(e *ExtensionElement) {
+// int.
-	addToSlice(&p.Extensions, e)
+func (p *Person) AddExtension(e *ExtensionElement) int {
+	return addToSlice(&p.Extensions, e)
 }
 
 // DeleteExtension deletes the Extension at index from the Person. It return an

plainText.go

@@ -16,7 +16,7 @@ func (p *PlainText) isText() bool { return true }
 // newPlainText creates a new PlainText. It returns a *PlainText.
 func newPlainText(textType, content string) *PlainText {
 	return &PlainText{
-		CommonAttributes: newCommonAttributes(),
+		CommonAttributes: NewCommonAttributes(),
 		Type:             textType,
 		Text:             content,
 	}

source.go

@@ -25,12 +25,13 @@ type Source struct {
 
 // NewSource creates a new Source. It returns a *Source.
 func NewSource() *Source {
-	return &Source{CommonAttributes: newCommonAttributes()}
+	return &Source{CommonAttributes: NewCommonAttributes()}
 }
 
-// AddAuthor adds the Person as an author to the Source.
+// AddAuthor adds the Person as an author to the Source. It returns its index as
-func (s *Source) AddAuthor(p *Person) {
+// an int.
-	addToSlice(&s.Authors, p)
+func (s *Source) AddAuthor(p *Person) int {
+	return addToSlice(&s.Authors, p)
 }
 
 // DeleteAuthor deletes the Person at index from the Source. It return an error.
@@ -41,9 +42,9 @@ func (s *Source) DeleteAuthor(index int) error {
 	return nil
 }
 
-// AddCategory adds the Category to the Source.
+// AddCategory adds the Category to the Source. It returns its index as an int.
-func (s *Source) AddCategory(c *Category) {
+func (s *Source) AddCategory(c *Category) int {
-	addToSlice(&s.Categories, c)
+	return addToSlice(&s.Categories, c)
 }
 
 // DeleteCategory deletes the Category at index from the Source. It return an
@@ -55,9 +56,10 @@ func (s *Source) DeleteCategory(index int) error {
 	return nil
 }
 
-// AddContributor adds the Person as a contributor to the Source.
+// AddContributor adds the Person as a contributor to the Source. It returns its
-func (s *Source) AddContributor(c *Person) {
+// index as an int.
-	addToSlice(&s.Contributors, c)
+func (s *Source) AddContributor(c *Person) int {
+	return addToSlice(&s.Contributors, c)
 }
 
 // DeleteContributor deletes the Person at index from the Source. It return an
@@ -69,9 +71,9 @@ func (s *Source) DeleteContributor(index int) error {
 	return nil
 }
 
-// AddLink adds the Link to the Source.
+// AddLink adds the Link to the Source. It returns its index as an int.
-func (s *Source) AddLink(l *Link) {
+func (s *Source) AddLink(l *Link) int {
-	addToSlice(&s.Links, l)
+	return addToSlice(&s.Links, l)
 }
 
 // DeleteLink deletes the Link at index from the Source. It return an error.
@@ -82,9 +84,10 @@ func (s *Source) DeleteLink(index int) error {
 	return nil
 }
 
-// AddExtension adds the ExtensionElement to the Source.
+// AddExtension adds the ExtensionElement to the Source. It returns its index as
-func (s *Source) AddExtension(e *ExtensionElement) {
+// an int.
-	addToSlice(&s.Extensions, e)
+func (s *Source) AddExtension(e *ExtensionElement) int {
+	return addToSlice(&s.Extensions, e)
 }
 
 // DeleteExtension deletes the Extension at index from the Source. It return an

xhtmlText.go

@@ -16,7 +16,7 @@ func (x *XHTMLText) isText() bool { return true }
 // newPlainText creates a new PlainText. It returns a *PlainText.
 func newXHTMLText(textType, content string) *XHTMLText {
 	return &XHTMLText{
-		CommonAttributes: newCommonAttributes(),
+		CommonAttributes: NewCommonAttributes(),
 		Type:             textType,
 		XHTMLDiv:         NewXHTMLDiv(content),
 	}