Add ability to define foreign keys in models

base.go

@@ -300,6 +300,15 @@ func (d *base) CreateTableSql(model *Model, ifNotExists bool) string {
 			a = append(a, ", ")
 		}
 	}
+	if len(model.ForeignKeys) > 0 {
+		a = append(a, ", ")
+	}
+	for i, fk := range model.ForeignKeys {
+		a = append(a, d.Dialect.ForeignKey(fk))
+		if i < len(model.ForeignKeys)-1 {
+			a = append(a, ", ")
+		}
+	}
 	a = append(a, " )")
 	return strings.Join(a, "")
 }
@@ -434,3 +443,30 @@ func (d *base) KeywordPrimaryKey() string {
 func (d *base) KeywordAutoIncrement() string {
 	return "AUTOINCREMENT"
 }
+
+func (d *base) ForeignKey(fk *ForeignKey) string {
+	return fmt.Sprintf(
+		"FOREIGN KEY (%v) REFERENCES %v(%v) ON UPDATE %v ON DELETE %v",
+		d.Dialect.Quote(fk.Column),
+		d.Dialect.Quote(fk.ReferenceTable),
+		d.Dialect.Quote(fk.ReferenceColumn),
+		d.Dialect.ReferentialAction(fk.OnUpdate),
+		d.Dialect.ReferentialAction(fk.OnDelete),
+	)
+
+}
+
+func (d *base) ReferentialAction(ra ReferentialAction) string {
+	switch ra {
+	case Cascade:
+		return "CASCADE"
+	case Restrict:
+		return "RESTRICT"
+	case NoAction:
+		return "NO ACTION"
+	case SetNull:
+		return "SET NULL"
+	}
+
+	return "NO ACTION"
+}

dialect.go

@@ -130,4 +130,10 @@ type Dialect interface {
 
 	// KeywordAutoIncrement returns the dialect specific keyword for 'AUTO_INCREMENT'.
 	KeywordAutoIncrement() string
+
+	// ForeignKey returns the dialect spefific foreign key constraint
+	ForeignKey(fk *ForeignKey) string
+
+	// ReferentialAction returns the dialect spefific foreign key referntial action
+	ReferentialAction(ra ReferentialAction) string
 }

hood.go

@@ -55,6 +55,19 @@ type (
 	// Indexes represents an array of indexes.
 	Indexes []*Index
 
+	// ForeignKey represents a foreign key
+	ForeignKey struct {
+		Name            string
+		Column          string
+		ReferenceTable  string
+		ReferenceColumn string
+		OnUpdate        ReferentialAction
+		OnDelete        ReferentialAction
+	}
+
+	// ForeignKeys represents an array of foreign keys
+	ForeignKeys []*ForeignKey
+
 	// Created denotes a timestamp field that is automatically set on insert.
 	Created struct {
 		time.Time
@@ -67,10 +80,11 @@ type (
 
 	// Model represents a parsed schema interface{}.
 	Model struct {
-		Pk      *ModelField
-		Table   string
-		Fields  []*ModelField
-		Indexes Indexes
+		Pk          *ModelField
+		Table       string
+		Fields      []*ModelField
+		Indexes     Indexes
+		ForeignKeys ForeignKeys
 	}
 
 	// ModelField represents a schema field of a parsed model.
@@ -100,6 +114,11 @@ type (
 		Indexes(indexes *Indexes)
 	}
 
+	// ForeignKeyed defines the foreign keys for a table.
+	ForeignKeyed interface {
+		ForeignKeys(foreignKeys *ForeignKeys)
+	}
+
 	// TODO: implement aggregate function types
 	//
 	// // Avg denotes an average aggregate function argument
@@ -150,6 +169,15 @@ const (
 
 type Join int
 
+const (
+	Cascade = ReferentialAction(iota)
+	Restrict
+	NoAction
+	SetNull
+)
+
+type ReferentialAction int
+
 // Add adds an index
 func (ix *Indexes) Add(name string, columns ...string) {
 	*ix = append(*ix, &Index{Name: name, Columns: columns, Unique: false})
@@ -160,6 +188,11 @@ func (ix *Indexes) AddUnique(name string, columns ...string) {
 	*ix = append(*ix, &Index{Name: name, Columns: columns, Unique: true})
 }
 
+// Add adds a foreign key
+func (fk *ForeignKeys) Add(name string, column string, referenceTable string, referenceColumn string, onUpdate ReferentialAction, onDelete ReferentialAction) {
+	*fk = append(*fk, &ForeignKey{Name: name, Column: column, ReferenceTable: referenceTable, ReferenceColumn: referenceColumn, OnUpdate: onUpdate, OnDelete: onDelete})
+}
+
 // Quote quotes the path using the given dialects Quote method
 func (p Path) Quote(d Dialect) string {
 	sep := "."
@@ -358,6 +391,18 @@ func (index *Index) GoDeclaration() string {
 	)
 }
 
+func (foreignKey *ForeignKey) GoDeclaration() string {
+	return fmt.Sprintf(
+		"foreignKeys.Add(\"%s\", \"%s\", \"%s\", \"%s\", %s, %s)",
+		foreignKey.Name,
+		foreignKey.Column,
+		foreignKey.ReferenceTable,
+		foreignKey.ReferenceColumn,
+		foreignKey.OnUpdate,
+		foreignKey.OnDelete,
+	)
+}
+
 func (model *Model) Validate() error {
 	for _, field := range model.Fields {
 		err := field.Validate()
@@ -384,6 +429,15 @@ func (model *Model) GoDeclaration() string {
 		}
 		a = append(a, "}")
 	}
+	if len(model.ForeignKeys) > 0 {
+		a = append(a,
+			fmt.Sprintf("\nfunc (table *%s) ForeignKeys(foreignKeys *hood.ForeignKeys) {", tableName),
+		)
+		for _, fk := range model.ForeignKeys {
+			a = append(a, "\t"+fk.GoDeclaration())
+		}
+		a = append(a, "}")
+	}
 	return strings.Join(a, "\n")
 }
 
@@ -1313,6 +1367,12 @@ func addIndexes(m *Model, f interface{}) {
 	}
 }
 
+func addForeignKeys(m *Model, f interface{}) {
+	if t, ok := f.(ForeignKeyed); ok {
+		t.ForeignKeys(&m.ForeignKeys)
+	}
+}
+
 func interfaceToModel(f interface{}) (*Model, error) {
 	v := reflect.Indirect(reflect.ValueOf(f))
 	if v.Kind() != reflect.Struct {
@@ -1327,6 +1387,7 @@ func interfaceToModel(f interface{}) (*Model, error) {
 	}
 	addFields(m, t, v)
 	addIndexes(m, f)
+	addForeignKeys(m, f)
 	return m, nil
 }