Initial commit

Author: junhuif

README.md

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+# Gorm Default Value
+
+Gorm takes the default value back from database after you create a new record with no value specified.
+
+## Quick Started 
+
+    # Get code
+    $ go get -u github.com/fengjh/gorm-default-value
+
+    # Set environment variables
+    $ source .env
+
+    # Setup postgres database
+    $ postgres=# CREATE USER gorm_default_value;
+    $ postgres=# CREATE DATABASE gorm_default_value OWNER gorm_default_value;
+
+    # Run Application
+    $ go test -v
+
+## Test Result
+
+    === RUN   TestCreateProductPriceWithDefaultValue
+    BeforeCreate --> 0
+    AfterCreate --> 0.01
+    BeforeCreateTransactionCommit --> 0.01
+    AfterCreateTransactionCommit --> 0.01
+    --- PASS: TestCreateProductPriceWithDefaultValue (0.00s)
+    === RUN   TestSaveProductPriceWithDefaultValue
+    BeforeCreate --> 0
+    AfterCreate --> 0.01
+    BeforeCreateTransactionCommit --> 0.01
+    AfterCreateTransactionCommit --> 0.01
+    --- PASS: TestSaveProductPriceWithDefaultValue (0.00s)
+    PASS
+    ok  	github.com/fengjh/gorm-default-value	0.072s

callbacks/callbacks.go

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+// Package callbacks extends default Gorm callbacks such as
+// executing callback after create transaction commit.
+package callbacks
+
+import "github.com/jinzhu/gorm"
+
+// CreateTransactionCommitCallback defines an interface
+// for executing callback before/after commit the create
+// transaction.
+type CreateTransactionCommitCallback interface {
+	BeforeCreateTransactionCommit(scope *gorm.Scope)
+	AfterCreateTransactionCommit(scope *gorm.Scope)
+}
+
+func beforeCreateTransaction(scope *gorm.Scope) {
+	if !scope.HasError() {
+		if createTransactionCommitCallback, ok := scope.Value.(CreateTransactionCommitCallback); ok {
+			createTransactionCommitCallback.BeforeCreateTransactionCommit(scope)
+		}
+	}
+}
+
+func afterCreateTransaction(scope *gorm.Scope) {
+	if !scope.HasError() {
+		if createTransactionCommitCallback, ok := scope.Value.(CreateTransactionCommitCallback); ok {
+			createTransactionCommitCallback.AfterCreateTransactionCommit(scope)
+		}
+	}
+}
+
+// RegisterCallbacks registers custom Gorm callbacks.
+func RegisterCallbacks(db *gorm.DB) {
+	callback := db.Callback()
+
+	callback.Create().Before("gorm:commit_or_rollback_transaction").Register("callbacks:before_create_transaction", beforeCreateTransaction)
+	callback.Create().After("gorm:commit_or_rollback_transaction").Register("callbacks:after_create_transaction", afterCreateTransaction)
+}

main.go

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+package main
+
+import (
+	"errors"
+	"fmt"
+	"os"
+
+	// Using postgres sql driver
+	_ "github.com/lib/pq"
+
+	"github.com/fengjh/gorm-default-value/callbacks"
+	"github.com/jinzhu/gorm"
+)
+
+var (
+	// DB returns a gorm.DB interface, it is used to access to database
+	DB *gorm.DB
+)
+
+type Product struct {
+	gorm.Model
+	Name     string  `sql:"not null"`
+	Price    float64 `sql:"not null;default:'0.01'"`
+	Category string  `sql:"not null;default:'clothing'"`
+}
+
+func (p *Product) BeforeCreate(scope *gorm.Scope) {
+	fmt.Printf("BeforeCreate --> %v\n", p.Price)
+	fmt.Printf("BeforeCreate --> %v\n", p.Category)
+}
+
+func (p *Product) AfterCreate(scope *gorm.Scope) {
+	fmt.Printf("AfterCreate --> %v\n", p.Price)
+	fmt.Printf("AfterCreate --> %v\n", p.Category)
+}
+
+func (p *Product) BeforeCreateTransactionCommit(scope *gorm.Scope) {
+	fmt.Printf("BeforeCreateTransactionCommit --> %v\n", p.Price)
+	fmt.Printf("BeforeCreateTransactionCommit --> %v\n", p.Category)
+}
+
+func (p *Product) AfterCreateTransactionCommit(scope *gorm.Scope) {
+	fmt.Printf("AfterCreateTransactionCommit --> %v\n", p.Price)
+	fmt.Printf("AfterCreateTransactionCommit --> %v\n", p.Category)
+}
+
+func init() {
+	initDB()
+	migrate()
+}
+
+func initDB() {
+	var err error
+	var db *gorm.DB
+
+	dbParams := os.Getenv("DB_PARAMS")
+	if dbParams == "" {
+		panic(errors.New("DB_PARAMS environment variable not set"))
+	}
+
+	db, err = gorm.Open("postgres", fmt.Sprintf(dbParams))
+	if err == nil {
+		DB = db
+	} else {
+		panic(err)
+	}
+
+	// Register custom Gorm callbacks
+	callbacks.RegisterCallbacks(DB)
+}
+
+func migrate() {
+	DB.DropTableIfExists(&Product{})
+	DB.AutoMigrate(&Product{})
+}

main_test.go

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+package main
+
+import (
+	"os"
+	"testing"
+)
+
+func TestMain(m *testing.M) {
+	initDB()
+	migrate()
+
+	retCode := m.Run()
+
+	os.Exit(retCode)
+}
+
+func TestCreateProductWithNoValueSpecified(t *testing.T) {
+	product := Product{Name: "Create product with no value specified"}
+
+	if product.Price != 0 {
+		t.Fatalf("expected new product's price is zero, but got %v", product.Price)
+	}
+
+	if product.Category != "" {
+		t.Fatalf("expected new product's category is zero, but got %v", product.Category)
+	}
+
+	err := DB.Create(&product).Error
+
+	if err != nil {
+		t.Fatalf("Unexpected error: %v", err)
+	}
+
+	if product.Price != 0.01 {
+		t.Fatalf("expected product.Price with default value 0.01, but got %v", product.Price)
+	}
+
+	if product.Category != "clothing" {
+		t.Fatalf("expected product.Price with default value clothing, but got %v", product.Category)
+	}
+}
+
+func TestSaveProductPriceWithNoValueSpecified(t *testing.T) {
+	product := Product{Name: "Save product with no value specified"}
+
+	if product.Price != 0 {
+		t.Fatalf("expected new product's price is zero, but got %v", product.Price)
+	}
+
+	if product.Category != "" {
+		t.Fatalf("expected new product's category is zero, but got %v", product.Category)
+	}
+
+	err := DB.Save(&product).Error
+
+	if err != nil {
+		t.Fatalf("Unexpected error: %v", err)
+	}
+
+	if product.Price != 0.01 {
+		t.Fatalf("expected product.Price with default value 0.01, but got %v", product.Price)
+	}
+
+	if product.Category != "clothing" {
+		t.Fatalf("expected product.Price with default value clothing, but got %v", product.Category)
+	}
+}
+
+func TestCreateProductPriceWithZeroValueSpecified(t *testing.T) {
+	product := Product{Name: "Product with zero value specified", Price: 0.0}
+
+	if product.Price != 0 {
+		t.Fatalf("expected new product's price is zero, but got %v", product.Price)
+	}
+
+	if product.Category != "" {
+		t.Fatalf("expected new product's category is zero, but got %v", product.Category)
+	}
+
+	err := DB.Create(&product).Error
+
+	if err != nil {
+		t.Fatalf("Unexpected error: %v", err)
+	}
+
+	if product.Price != 0.01 {
+		t.Fatalf("expected product.Price with default value 0.01, but got %v", product.Price)
+	}
+
+	if product.Category != "clothing" {
+		t.Fatalf("expected product.Price with default value clothing, but got %v", product.Category)
+	}
+}