Added more error handling and necessary functions

entry.go

@@ -2,6 +2,7 @@ package atom
 
 import (
 	"encoding/xml"
+	"errors"
 	"fmt"
 	"strings"
 	"time"
@@ -75,8 +76,12 @@ func NewEntry(title string) (*Entry, error) {
 	}, nil
 }
 
-// AddAuthor adds the Person as an author to the Entry.
-func (e *Entry) AddAuthor(p *Person) {
+// AddAuthor adds the Person as an author to the Entry. It returns an error.
+func (e *Entry) AddAuthor(p *Person) error {
+	if p == nil {
+		return errors.New("error adding author element to entry: *Person is nil")
+	}
+
 	if e.Authors == nil {
 		e.Authors = make([]*Person, 1)
 		e.Authors[0] = p
@@ -85,10 +90,15 @@ func (e *Entry) AddAuthor(p *Person) {
 	}
 
 	e.Updated.DateTime = DateTime(time.Now())
+	return nil
 }
 
-// AddCategory adds the Category to the Entry.
-func (e *Entry) AddCategory(c *Category) {
+// AddCategory adds the Category to the Entry. It returns an error.
+func (e *Entry) AddCategory(c *Category) error {
+	if c == nil {
+		return errors.New("error adding category element to entry: *Category is nil")
+	}
+
 	if e.Categories == nil {
 		e.Categories = make([]*Category, 1)
 		e.Categories[0] = c
@@ -97,10 +107,16 @@ func (e *Entry) AddCategory(c *Category) {
 	}
 
 	e.Updated.DateTime = DateTime(time.Now())
+	return nil
 }
 
-// AddContributor adds the Person as a contributor to the Entry.
-func (e *Entry) AddContributor(c *Person) {
+// AddContributor adds the Person as a contributor to the Entry. It returns an
+// error.
+func (e *Entry) AddContributor(c *Person) error {
+	if c == nil {
+		return errors.New("error adding contributor element to entry: *Person is nil")
+	}
+
 	if e.Contributors == nil {
 		e.Contributors = make([]*Person, 1)
 		e.Contributors[0] = c
@@ -109,10 +125,15 @@ func (e *Entry) AddContributor(c *Person) {
 	}
 
 	e.Updated.DateTime = DateTime(time.Now())
+	return nil
 }
 
-// AddLink adds the Link to the Entry.
-func (e *Entry) AddLink(l *Link) {
+// AddLink adds the Link to the Entry. It returns an error.
+func (e *Entry) AddLink(l *Link) error {
+	if l == nil {
+		return errors.New("error adding link element to entry: *Link is nil")
+	}
+
 	if e.Links == nil {
 		e.Links = make([]*Link, 1)
 		e.Links[0] = l
@@ -121,10 +142,15 @@ func (e *Entry) AddLink(l *Link) {
 	}
 
 	e.Updated.DateTime = DateTime(time.Now())
+	return nil
 }
 
-// AddExtension adds the ExtensionElement to the Entry.
-func (e *Entry) AddExtension(x *ExtensionElement) {
+// AddExtension adds the ExtensionElement to the Entry. It returns an error.
+func (e *Entry) AddExtension(x *ExtensionElement) error {
+	if x == nil {
+		return errors.New("error adding extension element to entry: *ExtensionElement is nil")
+	}
+
 	if e.Extensions == nil {
 		e.Extensions = make([]*ExtensionElement, 1)
 		e.Extensions[0] = x
@@ -133,6 +159,7 @@ func (e *Entry) AddExtension(x *ExtensionElement) {
 	}
 
 	e.Updated.DateTime = DateTime(time.Now())
+	return nil
 }
 
 // Check checks the Entry for incompatibilities with RFC4287. It returns an