Added Delete methods for slice elements to common attributes, entry, feed, person and source

commonAttributes.go

@@ -17,7 +17,7 @@ func newCommonAttributes() *CommonAttributes {
 	return new(CommonAttributes)
 }
 
-// AddAttribute adds the Attribute to the CommonAttributes.
+// AddAttribute adds the attribute to the CommonAttributes.
 func (c *CommonAttributes) AddAttribute(name, value string) {
 	if c.UndefinedAttributes == nil {
 		c.UndefinedAttributes = make([]*xml.Attr, 1)
@@ -27,6 +27,18 @@ func (c *CommonAttributes) AddAttribute(name, value string) {
 	}
 }
 
+// DeleteAttribute deletes the attribute from the CommonAttributes. It return an
+// error.
+func (c *CommonAttributes) DeleteAttribute(id int) error {
+	length := len(c.UndefinedAttributes)
+	if id > length {
+		return fmt.Errorf("error deleting undefined attribute from common attributes %v: id %v out of range %v", c, id, length)
+	}
+
+	c.UndefinedAttributes = append(c.UndefinedAttributes[:id], c.UndefinedAttributes[id+1:]...)
+	return nil
+}
+
 // Check checks the CommonAttributes for incompatibilities with RFC4287. It
 // returns an error.
 func (c *CommonAttributes) Check() error {

entry.go

@@ -39,16 +39,16 @@ func (e *Entry) checkAuthors(authorInFeed bool) error {
 	if e.Authors == nil {
 		if !authorInFeed {
 			if e.Source == nil {
-				return fmt.Errorf("no authors set in entry %v", e)
+				return fmt.Errorf("no authors set in entry %v", e.ID.URI)
 			}
 			if e.Source.Authors == nil {
-				return fmt.Errorf("no authors set in entry %v", e)
+				return fmt.Errorf("no authors set in entry %v", e.ID.URI)
 			}
 		}
 	} else {
 		for i, a := range e.Authors {
 			if err := a.Check(); err != nil {
-				return fmt.Errorf("author element %v of entry %v: %v", i, e, err)
+				return fmt.Errorf("author element %v of entry %v: %v", i, e.ID.URI, err)
 			}
 		}
 	}
@@ -75,7 +75,19 @@ func (e *Entry) AddAuthor(p *Person) {
 		e.Authors = append(e.Authors, p)
 	}
 
-	e.Updated.DateTime = DateTime(time.Now())
+	e.Updated = NewDate(time.Now())
+}
+
+// DeleteAuthor deletes the Person from the Entry. It return an error.
+func (e *Entry) DeleteAuthor(id int) error {
+	length := len(e.Authors)
+	if id > length {
+		return fmt.Errorf("error deleting author from entry %v: id %v out of range %v", e.ID.URI, id, length)
+	}
+
+	e.Authors = append(e.Authors[:id], e.Authors[id+1:]...)
+	e.Updated = NewDate(time.Now())
+	return nil
 }
 
 // AddCategory adds the Category to the Entry.
@@ -87,7 +99,19 @@ func (e *Entry) AddCategory(c *Category) {
 		e.Categories = append(e.Categories, c)
 	}
 
-	e.Updated.DateTime = DateTime(time.Now())
+	e.Updated = NewDate(time.Now())
+}
+
+// DeleteCategory deletes the Category from the Entry. It return an error.
+func (e *Entry) DeleteCategory(id int) error {
+	length := len(e.Categories)
+	if id > length {
+		return fmt.Errorf("error deleting category from entry %v: id %v out of range %v", e.ID.URI, id, length)
+	}
+
+	e.Categories = append(e.Categories[:id], e.Categories[id+1:]...)
+	e.Updated = NewDate(time.Now())
+	return nil
 }
 
 // AddContributor adds the Person as a contributor to the Entry.
@@ -99,7 +123,19 @@ func (e *Entry) AddContributor(c *Person) {
 		e.Contributors = append(e.Contributors, c)
 	}
 
-	e.Updated.DateTime = DateTime(time.Now())
+	e.Updated = NewDate(time.Now())
+}
+
+// DeleteContributor deletes the Person from the Entry. It return an error.
+func (e *Entry) DeleteContributor(id int) error {
+	length := len(e.Contributors)
+	if id > length {
+		return fmt.Errorf("error deleting contributor from entry %v: id %v out of range %v", e.ID.URI, id, length)
+	}
+
+	e.Contributors = append(e.Contributors[:id], e.Contributors[id+1:]...)
+	e.Updated = NewDate(time.Now())
+	return nil
 }
 
 // AddLink adds the Link to the Entry.
@@ -111,7 +147,19 @@ func (e *Entry) AddLink(l *Link) {
 		e.Links = append(e.Links, l)
 	}
 
-	e.Updated.DateTime = DateTime(time.Now())
+	e.Updated = NewDate(time.Now())
+}
+
+// DeleteLink deletes the Link from the Entry. It return an error.
+func (e *Entry) DeleteLink(id int) error {
+	length := len(e.Links)
+	if id > length {
+		return fmt.Errorf("error deleting link from entry %v: id %v out of range %v", e.ID.URI, id, length)
+	}
+
+	e.Links = append(e.Links[:id], e.Links[id+1:]...)
+	e.Updated = NewDate(time.Now())
+	return nil
 }
 
 // AddExtension adds the ExtensionElement to the Entry.
@@ -123,7 +171,19 @@ func (e *Entry) AddExtension(x *ExtensionElement) {
 		e.Extensions = append(e.Extensions, x)
 	}
 
-	e.Updated.DateTime = DateTime(time.Now())
+	e.Updated = NewDate(time.Now())
+}
+
+// DeleteExtension deletes the Extension from the Entry. It return an error.
+func (e *Entry) DeleteExtension(id int) error {
+	length := len(e.Extensions)
+	if id > length {
+		return fmt.Errorf("error deleting extension from entry %v: id %v out of range %v", e.ID.URI, id, length)
+	}
+
+	e.Extensions = append(e.Extensions[:id], e.Extensions[id+1:]...)
+	e.Updated = NewDate(time.Now())
+	return nil
 }
 
 // Check checks the Entry for incompatibilities with RFC4287. It returns an
@@ -138,64 +198,64 @@ func (e *Entry) Check() error {
 	}
 
 	if err := e.checkAuthors(true); err != nil {
-		return fmt.Errorf("entry %v: %v", e, err)
+		return fmt.Errorf("entry %v: %v", e.ID.URI, err)
 	}
 
 	for i, c := range e.Categories {
 		if err := c.Check(); err != nil {
-			return fmt.Errorf("category element %v of entry %v: %v", i, e, err)
+			return fmt.Errorf("category element %v of entry %v: %v", i, e.ID.URI, err)
 		}
 	}
 
 	if e.Content != nil {
 		if err := e.Content.Check(); err != nil {
-			return fmt.Errorf("content element of entry %v: %v", e, err)
+			return fmt.Errorf("content element of entry %v: %v", e.ID.URI, err)
 		}
 	} else {
 		// atom:entry elements that contain no child atom:content element MUST
 		// contain at least one atom:link element with a rel attribute value of
 		// "alternate".
 		if !alternateRelExists(e.Links) {
-			return fmt.Errorf("no content element of entry %v and no link element with rel \"alternate\"", e)
+			return fmt.Errorf("no content element of entry %v and no link element with rel \"alternate\"", e.ID.URI)
 		}
 	}
 
 	for i, c := range e.Contributors {
 		if err := c.Check(); err != nil {
-			return fmt.Errorf("contributor element %v of entry %v: %v", i, e, err)
+			return fmt.Errorf("contributor element %v of entry %v: %v", i, e.ID.URI, err)
 		}
 	}
 
 	for i, l := range e.Links {
 		if err := l.Check(); err != nil {
-			return fmt.Errorf("link element %v of entry %v: %v", i, e, err)
+			return fmt.Errorf("link element %v of entry %v: %v", i, e.ID.URI, err)
 		}
 	}
 	if hasAlternateDuplicateLinks(e.Links) {
-		return fmt.Errorf("links with a rel attribute value of \"alternate\" and duplicate type and hreflang attribute values found in entry %v", e)
+		return fmt.Errorf("links with a rel attribute value of \"alternate\" and duplicate type and hreflang attribute values found in entry %v", e.ID.URI)
 	}
 
 	if e.Published != nil {
 		if err := e.Published.Check(); err != nil {
-			return fmt.Errorf("published element of entry %v: %v", e, err)
+			return fmt.Errorf("published element of entry %v: %v", e.ID.URI, err)
 		}
 	}
 
 	if e.Rights != nil {
 		if err := e.Rights.Check(); err != nil {
-			return fmt.Errorf("rights element of entry %v: %v", e, err)
+			return fmt.Errorf("rights element of entry %v: %v", e.ID.URI, err)
 		}
 	}
 
 	if e.Source != nil {
 		if err := e.Source.Check(); err != nil {
-			return fmt.Errorf("source element of entry %v: %v", e, err)
+			return fmt.Errorf("source element of entry %v: %v", e.ID.URI, err)
 		}
 	}
 
 	if e.Summary != nil {
 		if err := e.Summary.Check(); err != nil {
-			return fmt.Errorf("summary element of entry %v: %v", e, err)
+			return fmt.Errorf("summary element of entry %v: %v", e.ID.URI, err)
 		}
 	} else {
 		// atom:entry elements MUST contain an atom:summary element in either
@@ -203,7 +263,7 @@ func (e *Entry) Check() error {
 		// the atom:entry contains an atom:content that has a "src" attribute
 		// (and is thus empty).
 		if e.Content.hasSRC() {
-			return fmt.Errorf("no summary element of entry %v but content of type out of line content", e)
+			return fmt.Errorf("no summary element of entry %v but content of type out of line content", e.ID.URI)
 		}
 		// the atom:entry contains content that is encoded in Base64; i.e., the
 		// "type" attribute of atom:content is a MIME media type [MIMEREG], but
@@ -211,29 +271,29 @@ func (e *Entry) Check() error {
 		// does not end with "/xml" or "+xml".
 		mediaType := e.Content.getType()
 		if isValidMediaType(mediaType) && !isXMLMediaType(mediaType) && !strings.HasPrefix(mediaType, "text/") {
-			return fmt.Errorf("no summary element of entry %v but media type not xml", e)
+			return fmt.Errorf("no summary element of entry %v but media type not xml", e.ID.URI)
 		}
 	}
 
 	if e.Title == nil {
-		return fmt.Errorf("no title element of entry %v", e)
+		return fmt.Errorf("no title element of entry %v", e.ID.URI)
 	} else {
 		if err := e.Title.Check(); err != nil {
-			return fmt.Errorf("title element of entry %v: %v", e, err)
+			return fmt.Errorf("title element of entry %v: %v", e.ID.URI, err)
 		}
 	}
 
 	if e.Updated == nil {
-		return fmt.Errorf("no updated element of entry %v", e)
+		return fmt.Errorf("no updated element of entry %v", e.ID.URI)
 	} else {
 		if err := e.Updated.Check(); err != nil {
-			return fmt.Errorf("updated element of entry %v: %v", e, err)
+			return fmt.Errorf("updated element of entry %v: %v", e.ID.URI, err)
 		}
 	}
 
 	for i, x := range e.Extensions {
 		if err := x.Check(); err != nil {
-			return fmt.Errorf("extension element %v of entry %v: %v", i, e, err)
+			return fmt.Errorf("extension element %v of entry %v: %v", i, e.ID.URI, err)
 		}
 	}
 
@@ -244,7 +304,7 @@ func (e *Entry) Check() error {
 func (e *Entry) ToXML(encoding string) (string, error) {
 	xml, err := xml.MarshalIndent(e, "", "  ")
 	if err != nil {
-		return "", fmt.Errorf("error xml encoding entry: %v", err)
+		return "", fmt.Errorf("error xml encoding entry %v: %v", e.ID.URI, err)
 	}
 
 	return fmt.Sprintln(`<?xml version="1.0" encoding="`+encoding+`"?>`) + string(xml), nil

feed.go

@@ -44,7 +44,19 @@ func (f *Feed) AddAuthor(p *Person) {
 		f.Authors = append(f.Authors, p)
 	}
 
-	f.Updated.DateTime = DateTime(time.Now())
+	f.Updated = NewDate(time.Now())
+}
+
+// DeleteAuthor deletes the Person from the Feed. It return an error.
+func (f *Feed) DeleteAuthor(id int) error {
+	length := len(f.Authors)
+	if id > length {
+		return fmt.Errorf("error deleting author from feed %v: id %v out of range %v", f.ID.URI, id, length)
+	}
+
+	f.Authors = append(f.Authors[:id], f.Authors[id+1:]...)
+	f.Updated = NewDate(time.Now())
+	return nil
 }
 
 // AddCategory adds the Category to the Feed.
@@ -56,7 +68,19 @@ func (f *Feed) AddCategory(c *Category) {
 		f.Categories = append(f.Categories, c)
 	}
 
-	f.Updated.DateTime = DateTime(time.Now())
+	f.Updated = NewDate(time.Now())
+}
+
+// DeleteCategory deletes the Category from the Feed. It return an error.
+func (f *Feed) DeleteCategory(id int) error {
+	length := len(f.Categories)
+	if id > length {
+		return fmt.Errorf("error deleting category from feed %v: id %v out of range %v", f.ID.URI, id, length)
+	}
+
+	f.Categories = append(f.Categories[:id], f.Categories[id+1:]...)
+	f.Updated = NewDate(time.Now())
+	return nil
 }
 
 // AddContributor adds the Person as a contributor to the Feed.
@@ -68,7 +92,19 @@ func (f *Feed) AddContributor(c *Person) {
 		f.Contributors = append(f.Contributors, c)
 	}
 
-	f.Updated.DateTime = DateTime(time.Now())
+	f.Updated = NewDate(time.Now())
+}
+
+// DeleteContributor deletes the Person from the Feed. It return an error.
+func (f *Feed) DeleteContributor(id int) error {
+	length := len(f.Contributors)
+	if id > length {
+		return fmt.Errorf("error deleting contributor from feed %v: id %v out of range %v", f.ID.URI, id, length)
+	}
+
+	f.Contributors = append(f.Contributors[:id], f.Contributors[id+1:]...)
+	f.Updated = NewDate(time.Now())
+	return nil
 }
 
 // AddLink adds the Link to the Feed. There should be one Link with Rel "self".
@@ -80,7 +116,19 @@ func (f *Feed) AddLink(l *Link) {
 		f.Links = append(f.Links, l)
 	}
 
-	f.Updated.DateTime = DateTime(time.Now())
+	f.Updated = NewDate(time.Now())
+}
+
+// DeleteLink deletes the Link from the Feed. It return an error.
+func (f *Feed) DeleteLink(id int) error {
+	length := len(f.Links)
+	if id > length {
+		return fmt.Errorf("error deleting link from feed %v: id %v out of range %v", f.ID.URI, id, length)
+	}
+
+	f.Links = append(f.Links[:id], f.Links[id+1:]...)
+	f.Updated = NewDate(time.Now())
+	return nil
 }
 
 // AddExtension adds the Extension to the Feed.
@@ -92,7 +140,19 @@ func (f *Feed) AddExtension(e *ExtensionElement) {
 		f.Extensions = append(f.Extensions, e)
 	}
 
-	f.Updated.DateTime = DateTime(time.Now())
+	f.Updated = NewDate(time.Now())
+}
+
+// DeleteExtension deletes the Extension from the Feed. It return an error.
+func (f *Feed) DeleteExtension(id int) error {
+	length := len(f.Extensions)
+	if id > length {
+		return fmt.Errorf("error deleting extension from feed %v: id %v out of range %v", f.ID.URI, id, length)
+	}
+
+	f.Extensions = append(f.Extensions[:id], f.Extensions[id+1:]...)
+	f.Updated = NewDate(time.Now())
+	return nil
 }
 
 // AddEntry adds the Entry to the Feed.
@@ -104,7 +164,41 @@ func (f *Feed) AddEntry(e *Entry) {
 		f.Entries = append(f.Entries, e)
 	}
 
-	f.Updated.DateTime = DateTime(time.Now())
+	f.Updated = NewDate(time.Now())
+}
+
+// DeleteEntry deletes the Entry from the Feed. It return an error.
+func (f *Feed) DeleteEntry(id int) error {
+	length := len(f.Entries)
+	if id > length {
+		return fmt.Errorf("error deleting entry from feed %v: id %v out of range %v", f.ID.URI, id, length)
+	}
+
+	f.Entries = append(f.Entries[:id], f.Entries[id+1:]...)
+	f.Updated = NewDate(time.Now())
+	return nil
+}
+
+// DeleteEntryByURI deletes the Entry from the Feed. It return an error.
+func (f *Feed) DeleteEntryByURI(uri string) error {
+	if !isValidIRI(uri) {
+		return fmt.Errorf("error deleting entry from feed %v: uri %v invalid", f.ID.URI, uri)
+	}
+
+	index := -1
+	for i, e := range f.Entries {
+		if e.ID.URI == uri {
+			index = i
+			break
+		}
+	}
+	if index < 0 {
+		return fmt.Errorf("error deleting entry from feed %v: id %v not found", f.ID.URI, uri)
+	}
+
+	f.Entries = append(f.Entries[:index], f.Entries[index+1:]...)
+	f.Updated = NewDate(time.Now())
+	return nil
 }
 
 // Check checks the Feed for incompatibilities with RFC4287. It returns an
@@ -124,93 +218,93 @@ func (f *Feed) Check() error {
 	if f.Authors == nil {
 		for _, e := range f.Entries {
 			if err := e.checkAuthors(false); err != nil {
-				return fmt.Errorf("no authors set in feed %v: %v", f, err)
+				return fmt.Errorf("no authors set in feed %v: %v", f.ID.URI, err)
 			}
 		}
 	} else {
 		for i, a := range f.Authors {
 			if err := a.Check(); err != nil {
-				return fmt.Errorf("author element %v of feed %v: %v", i, f, err)
+				return fmt.Errorf("author element %v of feed %v: %v", i, f.ID.URI, err)
 			}
 		}
 	}
 
 	for i, c := range f.Categories {
 		if err := c.Check(); err != nil {
-			return fmt.Errorf("category element %v of feed %v: %v", i, f, err)
+			return fmt.Errorf("category element %v of feed %v: %v", i, f.ID.URI, err)
 		}
 	}
 
 	for i, c := range f.Contributors {
 		if err := c.Check(); err != nil {
-			return fmt.Errorf("contributor element %v of feed %v: %v", i, f, err)
+			return fmt.Errorf("contributor element %v of feed %v: %v", i, f.ID.URI, err)
 		}
 	}
 
 	if f.Generator != nil {
 		if err := f.Generator.Check(); err != nil {
-			return fmt.Errorf("generator element of feed %v: %v", f, err)
+			return fmt.Errorf("generator element of feed %v: %v", f.ID.URI, err)
 		}
 	}
 
 	if f.Icon != nil {
 		if err := f.Icon.Check(); err != nil {
-			return fmt.Errorf("icon element of feed %v: %v", f, err)
+			return fmt.Errorf("icon element of feed %v: %v", f.ID.URI, err)
 		}
 	}
 
 	for i, l := range f.Links {
 		if err := l.Check(); err != nil {
-			return fmt.Errorf("link element %v of feed %v: %v", i, f, err)
+			return fmt.Errorf("link element %v of feed %v: %v", i, f.ID.URI, err)
 		}
 	}
 	if hasAlternateDuplicateLinks(f.Links) {
-		return fmt.Errorf("links with a rel attribute value of \"alternate\" and duplicate type and hreflang attribute values found in feed %v", f)
+		return fmt.Errorf("links with a rel attribute value of \"alternate\" and duplicate type and hreflang attribute values found in feed %v", f.ID.URI)
 	}
 
 	if f.Logo != nil {
 		if err := f.Logo.Check(); err != nil {
-			return fmt.Errorf("logo element of feed %v: %v", f, err)
+			return fmt.Errorf("logo element of feed %v: %v", f.ID.URI, err)
 		}
 	}
 
 	if f.Rights != nil {
 		if err := f.Rights.Check(); err != nil {
-			return fmt.Errorf("rights element of feed %v: %v", f, err)
+			return fmt.Errorf("rights element of feed %v: %v", f.ID.URI, err)
 		}
 	}
 
 	if f.Subtitle != nil {
 		if err := f.Subtitle.Check(); err != nil {
-			return fmt.Errorf("subtitle element of feed %v: %v", f, err)
+			return fmt.Errorf("subtitle element of feed %v: %v", f.ID.URI, err)
 		}
 	}
 
 	if f.Title == nil {
-		return fmt.Errorf("no title element of feed %v", f)
+		return fmt.Errorf("no title element of feed %v", f.ID.URI)
 	} else {
 		if err := f.Title.Check(); err != nil {
-			return fmt.Errorf("title element of feed %v: %v", f, err)
+			return fmt.Errorf("title element of feed %v: %v", f.ID.URI, err)
 		}
 	}
 
 	if f.Updated == nil {
-		return fmt.Errorf("no updated element of feed %v", f)
+		return fmt.Errorf("no updated element of feed %v", f.ID.URI)
 	} else {
 		if err := f.Updated.Check(); err != nil {
-			return fmt.Errorf("updated element of feed %v: %v", f, err)
+			return fmt.Errorf("updated element of feed %v: %v", f.ID.URI, err)
 		}
 	}
 
 	for i, x := range f.Extensions {
 		if err := x.Check(); err != nil {
-			return fmt.Errorf("extension element %v of feed %v: %v", i, f, err)
+			return fmt.Errorf("extension element %v of feed %v: %v", i, f.ID.URI, err)
 		}
 	}
 
 	for i, n := range f.Entries {
 		if err := n.Check(); err != nil {
-			return fmt.Errorf("entry element %v of feed %v: %v", i, f, err)
+			return fmt.Errorf("entry element %v of feed %v: %v", i, f.ID.URI, err)
 		}
 	}
 
@@ -221,7 +315,7 @@ func (f *Feed) Check() error {
 func (f *Feed) ToXML(encoding string) (string, error) {
 	xml, err := xml.MarshalIndent(f, "", "  ")
 	if err != nil {
-		return "", fmt.Errorf("error xml encoding feed: %v", err)
+		return "", fmt.Errorf("error xml encoding feed %v: %v", f.ID.URI, err)
 	}
 
 	return fmt.Sprintln(`<?xml version="1.0" encoding="`+encoding+`"?>`) + string(xml), nil

person.go

@@ -31,6 +31,17 @@ func (p *Person) AddExtension(e *ExtensionElement) {
 	}
 }
 
+// DeleteExtension deletes the Extension from the Person. It return an error.
+func (p *Person) DeleteExtension(id int) error {
+	length := len(p.Extensions)
+	if id > length {
+		return fmt.Errorf("error deleting extension from person %v: id %v out of range %v", p, id, length)
+	}
+
+	p.Extensions = append(p.Extensions[:id], p.Extensions[id+1:]...)
+	return nil
+}
+
 // Check checks the Person for incompatibilities with RFC4287. It returns an
 // error.
 func (p *Person) Check() error {
@@ -50,11 +61,9 @@ func (p *Person) Check() error {
 		}
 	}
 
-	if p.Extensions != nil {
+	for i, e := range p.Extensions {
-		for i, e := range p.Extensions {
+		if err := e.Check(); err != nil {
-			if err := e.Check(); err != nil {
+			return fmt.Errorf("extension element %v of person %v: %v", i, p, err)
-				return fmt.Errorf("extension element %v of person %v: %v", i, p, err)
-			}
 		}
 	}
 

source.go

@@ -28,7 +28,7 @@ func NewSource() *Source {
 	return &Source{CommonAttributes: newCommonAttributes()}
 }
 
-// AddAuthor adds the Person as an author to the Entry.
+// AddAuthor adds the Person as an author to the Source.
 func (s *Source) AddAuthor(p *Person) {
 	if s.Authors == nil {
 		s.Authors = make([]*Person, 1)
@@ -38,7 +38,18 @@ func (s *Source) AddAuthor(p *Person) {
 	}
 }
 
-// AddCategory adds the Category to the Entry.
+// DeleteAuthor deletes the Person from the Source. It return an error.
+func (s *Source) DeleteAuthor(id int) error {
+	length := len(s.Authors)
+	if id > length {
+		return fmt.Errorf("error deleting author from source %v: id %v out of range %v", s, id, length)
+	}
+
+	s.Authors = append(s.Authors[:id], s.Authors[id+1:]...)
+	return nil
+}
+
+// AddCategory adds the Category to the Source.
 func (s *Source) AddCategory(c *Category) {
 	if s.Categories == nil {
 		s.Categories = make([]*Category, 1)
@@ -48,7 +59,18 @@ func (s *Source) AddCategory(c *Category) {
 	}
 }
 
-// AddContributor adds the Person as a contributor to the Entry.
+// DeleteCategory deletes the Category from the Source. It return an error.
+func (s *Source) DeleteCategory(id int) error {
+	length := len(s.Categories)
+	if id > length {
+		return fmt.Errorf("error deleting category from source %v: id %v out of range %v", s, id, length)
+	}
+
+	s.Categories = append(s.Categories[:id], s.Categories[id+1:]...)
+	return nil
+}
+
+// AddContributor adds the Person as a contributor to the Source.
 func (s *Source) AddContributor(c *Person) {
 	if s.Contributors == nil {
 		s.Contributors = make([]*Person, 1)
@@ -58,7 +80,18 @@ func (s *Source) AddContributor(c *Person) {
 	}
 }
 
-// AddLink adds the Link to the Entry.
+// DeleteContributor deletes the Person from the Source. It return an error.
+func (s *Source) DeleteContributor(id int) error {
+	length := len(s.Contributors)
+	if id > length {
+		return fmt.Errorf("error deleting contributor from source %v: id %v out of range %v", s, id, length)
+	}
+
+	s.Contributors = append(s.Contributors[:id], s.Contributors[id+1:]...)
+	return nil
+}
+
+// AddLink adds the Link to the Source.
 func (s *Source) AddLink(l *Link) {
 	if s.Links == nil {
 		s.Links = make([]*Link, 1)
@@ -68,7 +101,18 @@ func (s *Source) AddLink(l *Link) {
 	}
 }
 
-// AddExtension adds the ExtensionElement to the Entry.
+// DeleteLink deletes the Link from the Source. It return an error.
+func (s *Source) DeleteLink(id int) error {
+	length := len(s.Links)
+	if id > length {
+		return fmt.Errorf("error deleting link from source %v: id %v out of range %v", s, id, length)
+	}
+
+	s.Links = append(s.Links[:id], s.Links[id+1:]...)
+	return nil
+}
+
+// AddExtension adds the ExtensionElement to the Source.
 func (s *Source) AddExtension(e *ExtensionElement) {
 	if s.Extensions == nil {
 		s.Extensions = make([]*ExtensionElement, 1)
@@ -78,6 +122,17 @@ func (s *Source) AddExtension(e *ExtensionElement) {
 	}
 }
 
+// DeleteExtension deletes the Extension from the Source. It return an error.
+func (s *Source) DeleteExtension(id int) error {
+	length := len(s.Extensions)
+	if id > length {
+		return fmt.Errorf("error deleting extension from source %v: id %v out of range %v", s, id, length)
+	}
+
+	s.Extensions = append(s.Extensions[:id], s.Extensions[id+1:]...)
+	return nil
+}
+
 // Check checks the Source for incompatibilities with RFC4287. It returns an
 // error.
 func (s *Source) Check() error {