Added more error handling and necessary functions

feed.go

@@ -2,6 +2,7 @@ package atom
 
 import (
 	"encoding/xml"
+	"errors"
 	"fmt"
 	"time"
 )
@@ -44,8 +45,12 @@ func NewFeed(title string) (*Feed, error) {
 	}, nil
 }
 
-// AddAuthor adds the Person as an author to the Feed.
-func (f *Feed) AddAuthor(p *Person) {
+// AddAuthor adds the Person as an author to the Feed. It returns an error.
+func (f *Feed) AddAuthor(p *Person) error {
+	if p == nil {
+		return errors.New("error adding author element to feed: *Person is nil")
+	}
+
 	if f.Authors == nil {
 		f.Authors = make([]*Person, 1)
 		f.Authors[0] = p
@@ -54,10 +59,15 @@ func (f *Feed) AddAuthor(p *Person) {
 	}
 
 	f.Updated.DateTime = DateTime(time.Now())
+	return nil
 }
 
-// AddCategory adds the Category to the Feed.
-func (f *Feed) AddCategory(c *Category) {
+// AddCategory adds the Category to the Feed. It returns an error.
+func (f *Feed) AddCategory(c *Category) error {
+	if c == nil {
+		return errors.New("error adding category element to feed: *Category is nil")
+	}
+
 	if f.Categories == nil {
 		f.Categories = make([]*Category, 1)
 		f.Categories[0] = c
@@ -66,10 +76,16 @@ func (f *Feed) AddCategory(c *Category) {
 	}
 
 	f.Updated.DateTime = DateTime(time.Now())
+	return nil
 }
 
-// AddContributor adds the Person as a contributor to the Feed.
-func (f *Feed) AddContributor(c *Person) {
+// AddContributor adds the Person as a contributor to the Feed. It returns an
+// error.
+func (f *Feed) AddContributor(c *Person) error {
+	if c == nil {
+		return errors.New("error adding contributor element to feed: *Person is nil")
+	}
+
 	if f.Contributors == nil {
 		f.Contributors = make([]*Person, 1)
 		f.Contributors[0] = c
@@ -78,10 +94,16 @@ func (f *Feed) AddContributor(c *Person) {
 	}
 
 	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) {
+// AddLink adds the Link to the Feed. It returns an error. There should be one
+// Link with Rel "self".
+func (f *Feed) AddLink(l *Link) error {
+	if l == nil {
+		return errors.New("error adding link element to feed: *Link is nil")
+	}
+
 	if f.Links == nil {
 		f.Links = make([]*Link, 1)
 		f.Links[0] = l
@@ -90,10 +112,15 @@ func (f *Feed) AddLink(l *Link) {
 	}
 
 	f.Updated.DateTime = DateTime(time.Now())
+	return nil
 }
 
-// AddExtension adds the Extension to the Feed.
-func (f *Feed) AddExtension(e *ExtensionElement) {
+// AddExtension adds the Extension to the Feed. It returns an error.
+func (f *Feed) AddExtension(e *ExtensionElement) error {
+	if e == nil {
+		return errors.New("error adding extension element to feed: *ExtensionElement is nil")
+	}
+
 	if f.Extensions == nil {
 		f.Extensions = make([]*ExtensionElement, 1)
 		f.Extensions[0] = e
@@ -102,10 +129,15 @@ func (f *Feed) AddExtension(e *ExtensionElement) {
 	}
 
 	f.Updated.DateTime = DateTime(time.Now())
+	return nil
 }
 
-// AddEntry adds the Entry to the Feed.
-func (f *Feed) AddEntry(e *Entry) {
+// AddEntry adds the Entry to the Feed. It returns an error.
+func (f *Feed) AddEntry(e *Entry) error {
+	if e == nil {
+		return errors.New("error adding entry element to feed: *Entry is nil")
+	}
+
 	if f.Entries == nil {
 		f.Entries = make([]*Entry, 1)
 		f.Entries[0] = e
@@ -114,6 +146,7 @@ func (f *Feed) AddEntry(e *Entry) {
 	}
 
 	f.Updated.DateTime = DateTime(time.Now())
+	return nil
 }
 
 // Check checks the Feed for incompatibilities with RFC4287. It returns an