Return the index of the added element

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
 
@@ -14,9 +14,9 @@ go get git.streifling.com/jason/atom@latest
 
 ## Usage
 
-This library provides convenient functions to safely create and extend elements
-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

atom.go

@@ -16,23 +16,25 @@ type Countable interface {
 	*xml.Attr | *Person | *Category | *Link | *ExtensionElement | *Entry
 }
 
-// addToSlice adds a Countable to to a *[]Countable
-func addToSlice[C Countable](slice *[]C, countable C) {
+// addToSlice adds a Countable to to a *[]Countable. It returns an int.
+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.
 // It return an error.
-func deleteFromSlice[C Countable](slice *[]C, id int) error {
+func deleteFromSlice[C Countable](slice *[]C, index int) error {
 	length := len(*slice)
-	if id > length {
-		return fmt.Errorf("id %v out of range %v", id, length)
+	if index > length {
+		return fmt.Errorf("id %v out of range %v", index, length)
 	}
 
-	*slice = append((*slice)[:id], (*slice)[id+1:]...)
+	*slice = append((*slice)[:index], (*slice)[index+1:]...)
 	return nil
 }
 

commonAttributes.go

@@ -17,16 +17,16 @@ func newCommonAttributes() *CommonAttributes {
 	return new(CommonAttributes)
 }
 
-// AddAttribute adds the attribute to the CommonAttributes.
-func (c *CommonAttributes) AddAttribute(name, value string) {
-	addToSlice(&c.UndefinedAttributes, &xml.Attr{Name: xml.Name{Local: name}, Value: value})
+// AddAttribute adds the attribute to the CommonAttributes. It returns an int.
+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 from the CommonAttributes. It return an
-// error.
-func (c *CommonAttributes) DeleteAttribute(id int) error {
-	if err := deleteFromSlice(&c.UndefinedAttributes, id); err != nil {
-		return fmt.Errorf("error deleting undefined attribute %v from common attributes %v: %v", id, c, err)
+// DeleteAttribute deletes the attribute at index from the CommonAttributes. It
+// return an error.
+func (c *CommonAttributes) DeleteAttribute(index int) error {
+	if err := deleteFromSlice(&c.UndefinedAttributes, index); err != nil {
+		return fmt.Errorf("error deleting undefined attribute %v from common attributes %v: %v", index, c, err)
 	}
 	return nil
 }

entry.go

@@ -66,80 +66,84 @@ func NewEntry(title string) *Entry {
 	}
 }
 
-// AddAuthor adds the Person as an author to the Entry.
-func (e *Entry) AddAuthor(p *Person) {
-	addToSlice(&e.Authors, p)
+// AddAuthor adds the Person as an author to the Entry. It returns an int.
+func (e *Entry) AddAuthor(p *Person) int {
 	e.Updated = NewDate(time.Now())
+	return addToSlice(&e.Authors, p)
 }
 
-// DeleteAuthor deletes the Person from the Entry. It return an error.
-func (e *Entry) DeleteAuthor(id int) error {
-	if err := deleteFromSlice(&e.Authors, id); err != nil {
-		return fmt.Errorf("error deleting author %v from entry %v: %v", id, e.ID.URI, err)
+// DeleteAuthor deletes the Person at index from the Entry. It return an error.
+func (e *Entry) DeleteAuthor(index int) error {
+	if err := deleteFromSlice(&e.Authors, index); err != nil {
+		return fmt.Errorf("error deleting author %v from entry %v: %v", index, e.ID.URI, err)
 	}
 
 	e.Updated = NewDate(time.Now())
 	return nil
 }
 
-// AddCategory adds the Category to the Entry.
-func (e *Entry) AddCategory(c *Category) {
-	addToSlice(&e.Categories, c)
+// AddCategory adds the Category to the Entry. It returns an int.
+func (e *Entry) AddCategory(c *Category) int {
 	e.Updated = NewDate(time.Now())
+	return addToSlice(&e.Categories, c)
 }
 
-// DeleteCategory deletes the Category from the Entry. It return an error.
-func (e *Entry) DeleteCategory(id int) error {
-	if err := deleteFromSlice(&e.Categories, id); err != nil {
-		return fmt.Errorf("error deleting category %v from entry %v: %v", id, e.ID.URI, err)
+// DeleteCategory deletes the Category at index from the Entry. It return an
+// error.
+func (e *Entry) DeleteCategory(index int) error {
+	if err := deleteFromSlice(&e.Categories, index); err != nil {
+		return fmt.Errorf("error deleting category %v from entry %v: %v", index, e.ID.URI, err)
 	}
 
 	e.Updated = NewDate(time.Now())
 	return nil
 }
 
-// AddContributor adds the Person as a contributor to the Entry.
-func (e *Entry) AddContributor(c *Person) {
-	addToSlice(&e.Contributors, c)
+// AddContributor adds the Person as a contributor to the Entry. It returns an
+// int.
+func (e *Entry) AddContributor(c *Person) int {
 	e.Updated = NewDate(time.Now())
+	return addToSlice(&e.Contributors, c)
 }
 
-// DeleteContributor deletes the Person from the Entry. It return an error.
-func (e *Entry) DeleteContributor(id int) error {
-	if err := deleteFromSlice(&e.Contributors, id); err != nil {
-		return fmt.Errorf("error deleting contributor %v from entry %v: %v", id, e.ID.URI, err)
+// DeleteContributor deletes the Person at index from the Entry. It return an
+// error.
+func (e *Entry) DeleteContributor(index int) error {
+	if err := deleteFromSlice(&e.Contributors, index); err != nil {
+		return fmt.Errorf("error deleting contributor %v from entry %v: %v", index, e.ID.URI, err)
 	}
 
 	e.Updated = NewDate(time.Now())
 	return nil
 }
 
-// AddLink adds the Link to the Entry.
-func (e *Entry) AddLink(l *Link) {
-	addToSlice(&e.Links, l)
+// AddLink adds the Link to the Entry. It returns an int.
+func (e *Entry) AddLink(l *Link) int {
 	e.Updated = NewDate(time.Now())
+	return addToSlice(&e.Links, l)
 }
 
-// DeleteLink deletes the Link from the Entry. It return an error.
-func (e *Entry) DeleteLink(id int) error {
-	if err := deleteFromSlice(&e.Links, id); err != nil {
-		return fmt.Errorf("error deleting link %v from entry %v: %v", id, e.ID.URI, err)
+// DeleteLink deletes the Link at index from the Entry. It return an error.
+func (e *Entry) DeleteLink(index int) error {
+	if err := deleteFromSlice(&e.Links, index); err != nil {
+		return fmt.Errorf("error deleting link %v from entry %v: %v", index, e.ID.URI, err)
 	}
 
 	e.Updated = NewDate(time.Now())
 	return nil
 }
 
-// AddExtension adds the ExtensionElement to the Entry.
-func (e *Entry) AddExtension(x *ExtensionElement) {
-	addToSlice(&e.Extensions, x)
+// AddExtension adds the ExtensionElement to the Entry. It returns an int.
+func (e *Entry) AddExtension(x *ExtensionElement) int {
 	e.Updated = NewDate(time.Now())
+	return addToSlice(&e.Extensions, x)
 }
 
-// DeleteExtension deletes the Extension from the Entry. It return an error.
-func (e *Entry) DeleteExtension(id int) error {
-	if err := deleteFromSlice(&e.Extensions, id); err != nil {
-		return fmt.Errorf("error deleting extension %v from entry %v: %v", id, e.ID.URI, err)
+// DeleteExtension deletes the Extension at index from the Entry. It return an
+// error.
+func (e *Entry) DeleteExtension(index int) error {
+	if err := deleteFromSlice(&e.Extensions, index); err != nil {
+		return fmt.Errorf("error deleting extension %v from entry %v: %v", index, e.ID.URI, err)
 	}
 
 	e.Updated = NewDate(time.Now())

feed.go

@@ -35,48 +35,51 @@ func NewFeed(title string) *Feed {
 	}
 }
 
-// AddAuthor adds the Person as an author to the Feed.
-func (f *Feed) AddAuthor(p *Person) {
-	addToSlice(&f.Authors, p)
+// AddAuthor adds the Person as an author to the Feed. It returns an int.
+func (f *Feed) AddAuthor(p *Person) int {
 	f.Updated = NewDate(time.Now())
+	return addToSlice(&f.Authors, p)
 }
 
-// DeleteAuthor deletes the Person from the Feed. It return an error.
-func (f *Feed) DeleteAuthor(id int) error {
-	if err := deleteFromSlice(&f.Authors, id); err != nil {
-		return fmt.Errorf("error deleting author %v from entry %v: %v", id, f.ID.URI, err)
+// DeleteAuthor deletes the Person at index from the Feed. It return an error.
+func (f *Feed) DeleteAuthor(index int) error {
+	if err := deleteFromSlice(&f.Authors, index); err != nil {
+		return fmt.Errorf("error deleting author %v from entry %v: %v", index, f.ID.URI, err)
 	}
 
 	f.Updated = NewDate(time.Now())
 	return nil
 }
 
-// AddCategory adds the Category to the Feed.
-func (f *Feed) AddCategory(c *Category) {
-	addToSlice(&f.Categories, c)
+// AddCategory adds the Category to the Feed. It returns an int.
+func (f *Feed) AddCategory(c *Category) int {
 	f.Updated = NewDate(time.Now())
+	return addToSlice(&f.Categories, c)
 }
 
-// DeleteCategory deletes the Category from the Feed. It return an error.
-func (f *Feed) DeleteCategory(id int) error {
-	if err := deleteFromSlice(&f.Categories, id); err != nil {
-		return fmt.Errorf("error deleting category %v from entry %v: %v", id, f.ID.URI, err)
+// DeleteCategory deletes the Category at index from the Feed. It return an
+// error.
+func (f *Feed) DeleteCategory(index int) error {
+	if err := deleteFromSlice(&f.Categories, index); err != nil {
+		return fmt.Errorf("error deleting category %v from entry %v: %v", index, f.ID.URI, err)
 	}
 
 	f.Updated = NewDate(time.Now())
 	return nil
 }
 
-// AddContributor adds the Person as a contributor to the Feed.
-func (f *Feed) AddContributor(c *Person) {
-	addToSlice(&f.Contributors, c)
+// AddContributor adds the Person as a contributor to the Feed. It returns an
+// int.
+func (f *Feed) AddContributor(c *Person) int {
 	f.Updated = NewDate(time.Now())
+	return addToSlice(&f.Contributors, c)
 }
 
-// DeleteContributor deletes the Person from the Feed. It return an error.
-func (f *Feed) DeleteContributor(id int) error {
-	if err := deleteFromSlice(&f.Contributors, id); err != nil {
-		return fmt.Errorf("error deleting contributor %v from entry %v: %v", id, f.ID.URI, err)
+// DeleteContributor deletes the Person at index from the Feed. It return an
+// error.
+func (f *Feed) DeleteContributor(index int) error {
+	if err := deleteFromSlice(&f.Contributors, index); err != nil {
+		return fmt.Errorf("error deleting contributor %v from entry %v: %v", index, f.ID.URI, err)
 	}
 
 	f.Updated = NewDate(time.Now())
@@ -84,47 +87,49 @@ func (f *Feed) DeleteContributor(id int) error {
 }
 
 // AddLink adds the Link to the Feed. There should be one Link with Rel "self".
-func (f *Feed) AddLink(l *Link) {
-	addToSlice(&f.Links, l)
+// It returns an int.
+func (f *Feed) AddLink(l *Link) int {
 	f.Updated = NewDate(time.Now())
+	return addToSlice(&f.Links, l)
 }
 
-// DeleteLink deletes the Link from the Feed. It return an error.
-func (f *Feed) DeleteLink(id int) error {
-	if err := deleteFromSlice(&f.Links, id); err != nil {
-		return fmt.Errorf("error deleting link %v from entry %v: %v", id, f.ID.URI, err)
+// DeleteLink deletes the Link at index from the Feed. It return an error.
+func (f *Feed) DeleteLink(index int) error {
+	if err := deleteFromSlice(&f.Links, index); err != nil {
+		return fmt.Errorf("error deleting link %v from entry %v: %v", index, f.ID.URI, err)
 	}
 
 	f.Updated = NewDate(time.Now())
 	return nil
 }
 
-// AddExtension adds the Extension to the Feed.
-func (f *Feed) AddExtension(e *ExtensionElement) {
-	addToSlice(&f.Extensions, e)
+// AddExtension adds the Extension to the Feed. It returns an int.
+func (f *Feed) AddExtension(e *ExtensionElement) int {
 	f.Updated = NewDate(time.Now())
+	return addToSlice(&f.Extensions, e)
 }
 
-// DeleteExtension deletes the Extension from the Feed. It return an error.
-func (f *Feed) DeleteExtension(id int) error {
-	if err := deleteFromSlice(&f.Extensions, id); err != nil {
-		return fmt.Errorf("error deleting extension %v from entry %v: %v", id, f.ID.URI, err)
+// DeleteExtension deletes the Extension at index from the Feed. It return an
+// error.
+func (f *Feed) DeleteExtension(index int) error {
+	if err := deleteFromSlice(&f.Extensions, index); err != nil {
+		return fmt.Errorf("error deleting extension %v from entry %v: %v", index, f.ID.URI, err)
 	}
 
 	f.Updated = NewDate(time.Now())
 	return nil
 }
 
-// AddEntry adds the Entry to the Feed.
-func (f *Feed) AddEntry(e *Entry) {
-	addToSlice(&f.Entries, e)
+// AddEntry adds the Entry to the Feed. It returns an int.
+func (f *Feed) AddEntry(e *Entry) int {
 	f.Updated = NewDate(time.Now())
+	return addToSlice(&f.Entries, e)
 }
 
-// DeleteEntry deletes the Entry from the Feed. It return an error.
-func (f *Feed) DeleteEntry(id int) error {
-	if err := deleteFromSlice(&f.Entries, id); err != nil {
-		return fmt.Errorf("error deleting entry %v from entry %v: %v", id, f.ID.URI, err)
+// DeleteEntry deletes the Entry at index from the Feed. It return an error.
+func (f *Feed) DeleteEntry(index int) error {
+	if err := deleteFromSlice(&f.Entries, index); err != nil {
+		return fmt.Errorf("error deleting entry %v from entry %v: %v", index, f.ID.URI, err)
 	}
 
 	f.Updated = NewDate(time.Now())

person.go

@@ -21,15 +21,16 @@ func NewPerson(name string) *Person {
 	}
 }
 
-// AddExtension adds the Extension to the Person.
-func (p *Person) AddExtension(e *ExtensionElement) {
-	addToSlice(&p.Extensions, e)
+// AddExtension adds the Extension to the Person. It returns an int.
+func (p *Person) AddExtension(e *ExtensionElement) int {
+	return addToSlice(&p.Extensions, e)
 }
 
-// DeleteExtension deletes the Extension from the Person. It return an error.
-func (p *Person) DeleteExtension(id int) error {
-	if err := deleteFromSlice(&p.Extensions, id); err != nil {
-		return fmt.Errorf("error deleting extension %v from person %v: %v", id, p, err)
+// DeleteExtension deletes the Extension at index from the Person. It return an
+// error.
+func (p *Person) DeleteExtension(index int) error {
+	if err := deleteFromSlice(&p.Extensions, index); err != nil {
+		return fmt.Errorf("error deleting extension %v from person %v: %v", index, p, err)
 	}
 	return nil
 }

source.go

@@ -28,67 +28,71 @@ func NewSource() *Source {
 	return &Source{CommonAttributes: newCommonAttributes()}
 }
 
-// AddAuthor adds the Person as an author to the Source.
-func (s *Source) AddAuthor(p *Person) {
-	addToSlice(&s.Authors, p)
+// AddAuthor adds the Person as an author to the Source. It returns an int.
+func (s *Source) AddAuthor(p *Person) int {
+	return addToSlice(&s.Authors, p)
 }
 
-// DeleteAuthor deletes the Person from the Source. It return an error.
-func (s *Source) DeleteAuthor(id int) error {
-	if err := deleteFromSlice(&s.Authors, id); err != nil {
-		return fmt.Errorf("error deleting author %v from source %v: %v", id, s, err)
+// DeleteAuthor deletes the Person at index from the Source. It return an error.
+func (s *Source) DeleteAuthor(index int) error {
+	if err := deleteFromSlice(&s.Authors, index); err != nil {
+		return fmt.Errorf("error deleting author %v from source %v: %v", index, s, err)
 	}
 	return nil
 }
 
-// AddCategory adds the Category to the Source.
-func (s *Source) AddCategory(c *Category) {
-	addToSlice(&s.Categories, c)
+// AddCategory adds the Category to the Source. It returns an int.
+func (s *Source) AddCategory(c *Category) int {
+	return addToSlice(&s.Categories, c)
 }
 
-// DeleteCategory deletes the Category from the Source. It return an error.
-func (s *Source) DeleteCategory(id int) error {
-	if err := deleteFromSlice(&s.Categories, id); err != nil {
-		return fmt.Errorf("error deleting category %v from source %v: %v", id, s, err)
+// DeleteCategory deletes the Category at index from the Source. It return an
+// error.
+func (s *Source) DeleteCategory(index int) error {
+	if err := deleteFromSlice(&s.Categories, index); err != nil {
+		return fmt.Errorf("error deleting category %v from source %v: %v", index, s, err)
 	}
 	return nil
 }
 
-// AddContributor adds the Person as a contributor to the Source.
-func (s *Source) AddContributor(c *Person) {
-	addToSlice(&s.Contributors, c)
+// AddContributor adds the Person as a contributor to the Source. It returns an
+// int.
+func (s *Source) AddContributor(c *Person) int {
+	return addToSlice(&s.Contributors, c)
 }
 
-// DeleteContributor deletes the Person from the Source. It return an error.
-func (s *Source) DeleteContributor(id int) error {
-	if err := deleteFromSlice(&s.Contributors, id); err != nil {
-		return fmt.Errorf("error deleting contributor %v from source %v: %v", id, s, err)
+// DeleteContributor deletes the Person at index from the Source. It return an
+// error.
+func (s *Source) DeleteContributor(index int) error {
+	if err := deleteFromSlice(&s.Contributors, index); err != nil {
+		return fmt.Errorf("error deleting contributor %v from source %v: %v", index, s, err)
 	}
 	return nil
 }
 
-// AddLink adds the Link to the Source.
-func (s *Source) AddLink(l *Link) {
-	addToSlice(&s.Links, l)
+// AddLink adds the Link to the Source. It returns an int.
+func (s *Source) AddLink(l *Link) int {
+	return addToSlice(&s.Links, l)
 }
 
-// DeleteLink deletes the Link from the Source. It return an error.
-func (s *Source) DeleteLink(id int) error {
-	if err := deleteFromSlice(&s.Links, id); err != nil {
-		return fmt.Errorf("error deleting link %v from source %v: %v", id, s, err)
+// DeleteLink deletes the Link at index from the Source. It return an error.
+func (s *Source) DeleteLink(index int) error {
+	if err := deleteFromSlice(&s.Links, index); err != nil {
+		return fmt.Errorf("error deleting link %v from source %v: %v", index, s, err)
 	}
 	return nil
 }
 
-// AddExtension adds the ExtensionElement to the Source.
-func (s *Source) AddExtension(e *ExtensionElement) {
-	addToSlice(&s.Extensions, e)
+// AddExtension adds the ExtensionElement to the Source. It returns an int.
+func (s *Source) AddExtension(e *ExtensionElement) int {
+	return addToSlice(&s.Extensions, e)
 }
 
-// DeleteExtension deletes the Extension from the Source. It return an error.
-func (s *Source) DeleteExtension(id int) error {
-	if err := deleteFromSlice(&s.Extensions, id); err != nil {
-		return fmt.Errorf("error deleting extension %v from source %v: %v", id, s, err)
+// DeleteExtension deletes the Extension at index from the Source. It return an
+// error.
+func (s *Source) DeleteExtension(index int) error {
+	if err := deleteFromSlice(&s.Extensions, index); err != nil {
+		return fmt.Errorf("error deleting extension %v from source %v: %v", index, s, err)
 	}
 	return nil
 }