Implement sort.Interface to required struct slice

aliasdomain.go

@@ -6,6 +6,13 @@ type AliasDomain struct {
 	target string
 }
 
+// AliasDomainSlice attaches the methods of sort.Interface to []*AliasDomain.
+type AliasDomainSlice []*AliasDomain
+
+func (p AliasDomainSlice) Len() int           { return len(p) }
+func (p AliasDomainSlice) Less(i, j int) bool { return p[i].Name() < p[j].Name() }
+func (p AliasDomainSlice) Swap(i, j int)      { p[i], p[j] = p[j], p[i] }
+
 // NewAliasDomain creates a new AliasDomain instance.
 func NewAliasDomain(name, target string) (*AliasDomain, error) {
 	if !validAliasDomainName(name) {

aliasuser.go

@@ -13,6 +13,13 @@ type AliasUser struct {
 	targets []string
 }
 
+// AliasUserSlice attaches the methods of sort.Interface to []*AliasUser.
+type AliasUserSlice []*AliasUser
+
+func (p AliasUserSlice) Len() int           { return len(p) }
+func (p AliasUserSlice) Less(i, j int) bool { return p[i].Name() < p[j].Name() }
+func (p AliasUserSlice) Swap(i, j int)      { p[i], p[j] = p[j], p[i] }
+
 // NewAliasUser creates a new AliasUser instance.
 func NewAliasUser(name string, targets []string) (*AliasUser, error) {
 	if !validAliasUserName(name) {

domain.go

@@ -8,6 +8,13 @@ type Domain struct {
 	CatchAllUser *CatchAllUser
 }
 
+// DomainSlice attaches the methods of sort.Interface to []*Domain.
+type DomainSlice []*Domain
+
+func (p DomainSlice) Len() int           { return len(p) }
+func (p DomainSlice) Less(i, j int) bool { return p[i].Name() < p[j].Name() }
+func (p DomainSlice) Swap(i, j int)      { p[i], p[j] = p[j], p[i] }
+
 // NewDomain creates a new Domain instance.
 func NewDomain(name string) (*Domain, error) {
 	if !validDomainName(name) {

user.go

@@ -7,6 +7,13 @@ type User struct {
 	forwards       []string
 }
 
+// UserSlice attaches the methods of sort.Interface to []*User.
+type UserSlice []*User
+
+func (p UserSlice) Len() int           { return len(p) }
+func (p UserSlice) Less(i, j int) bool { return p[i].Name() < p[j].Name() }
+func (p UserSlice) Swap(i, j int)      { p[i], p[j] = p[j], p[i] }
+
 // NewUser creates a new User instance.
 func NewUser(name, hashedPassword string, forwards []string) (*User, error) {
 	if !validUserName(name) {