improve gconv.Bool for NO/YES; improve gdb for model generation

.example/database/gdb/mysql/config.toml

@@ -1,5 +1,5 @@
 
 # MySQL数据库配置
 [database]
-    link = "mysql:luoling2013:m5k2s8p5@tcp(127.0.0.1:3306)/test"
+    link = "mysql:root:12345678@tcp(127.0.0.1:3306)/test"
 

.example/database/gdb/mysql/gdb_tables.go

@@ -0,0 +1,18 @@
+package main
+
+import (
+	"github.com/gogf/gf/frame/g"
+)
+
+func main() {
+	db := g.DB()
+	db.SetDebug(true)
+
+	tables, err := db.Tables()
+	if err != nil {
+		panic(err)
+	}
+	if tables != nil {
+		g.Dump(tables)
+	}
+}

.example/database/gdb/mysql/gdb_tables_fields.go

@@ -0,0 +1,25 @@
+package main
+
+import (
+	"github.com/gogf/gf/frame/g"
+)
+
+func main() {
+	db := g.DB()
+	db.SetDebug(true)
+
+	tables, e := db.Tables()
+	if e != nil {
+		panic(e)
+	}
+	if tables != nil {
+		g.Dump(tables)
+		for _, table := range tables {
+			fields, err := db.TableFields(table)
+			if err != nil {
+				panic(err)
+			}
+			g.Dump(fields)
+		}
+	}
+}

.example/frame/mvc/model/test/init.go

@@ -1,10 +1,8 @@
 package test
 
-import (
-	"github.com/gogf/gf/database/gdb"
-	"github.com/gogf/gf/frame/g"
-)
+import "github.com/gogf/gf/database/gdb"
 
-func DB() gdb.DB {
-	return g.DB()
-}
+var (
+	// ConfigGroup is the configuration group name for this model.
+	ConfigGroup = gdb.DEFAULT_GROUP_NAME
+)

.example/frame/mvc/model/test/user.go

@@ -3,13 +3,13 @@ package test
 import (
 	"database/sql"
 
-	"github.com/gogf/gf/debug/gdebug"
-	"github.com/gogf/gf/frame/gins"
+	"github.com/gogf/gf/frame/g"
 
 	"github.com/gogf/gf/database/gdb"
 	"github.com/gogf/gf/os/gtime"
 )
 
+// User is the golang structure for table user.
 type User struct {
 	Id         int         `orm:"id,primary"  json:"id"`
 	Passport   string      `orm:"passport"    json:"passport"`
@@ -18,50 +18,59 @@ type User struct {
 	CreateTime *gtime.Time `orm:"create_time" json:"create_time"`
 }
 
+// UserModel is the model of convenient operations for table user.
 type UserModel struct {
 	*gdb.Model
 	TableName string
 }
 
 var (
-	UserTableName      = "user"
-	gUserModelCacheKey = gdebug.CallerFilePath()
+	// UserTableName is the table name of user.
+	UserTableName = "user"
 )
 
+// ModelUser creates and returns a new model object for table user.
 func ModelUser() *UserModel {
-	return gins.GetOrSetFunc(gUserModelCacheKey, func() interface{} {
-		return &UserModel{
-			DB().Table(UserTableName).Safe(),
-			UserTableName,
-		}
-	}).(*UserModel)
+	return &UserModel{
+		g.DB(ConfigGroup).Table(UserTableName).Safe(),
+		UserTableName,
+	}
 }
 
+// Inserts does "INSERT...INTO..." statement for inserting current object into table.
 func (r *User) Insert() (result sql.Result, err error) {
 	return ModelUser().Data(r).Insert()
 }
 
+// Replace does "REPLACE...INTO..." statement for inserting current object into table.
+// If there's already another same record in the table (it checks using primary key or unique index),
+// it deletes it and insert this one.
 func (r *User) Replace() (result sql.Result, err error) {
 	return ModelUser().Data(r).Replace()
 }
 
+// Save does "INSERT...INTO..." statement for inserting/updating current object into table.
+// It updates the record if there's already another same record in the table
+// (it checks using primary key or unique index).
 func (r *User) Save() (result sql.Result, err error) {
 	return ModelUser().Data(r).Save()
 }
 
+// Update does "UPDATE...WHERE..." statement for updating current object from table.
+// It updates the record if there's already another same record in the table
+// (it checks using primary key or unique index).
 func (r *User) Update() (result sql.Result, err error) {
 	return ModelUser().Data(r).Where(gdb.GetWhereConditionOfStruct(r)).Update()
 }
 
+// Delete does "DELETE FROM...WHERE..." statement for deleting current object from table.
 func (r *User) Delete() (result sql.Result, err error) {
 	return ModelUser().Where(gdb.GetWhereConditionOfStruct(r)).Delete()
 }
 
+// Select overwrite the Select method from gdb.Model for model
+// as retuning all objects with specified structure.
 func (m *UserModel) Select() ([]*User, error) {
-	return m.All()
-}
-
-func (m *UserModel) All() ([]*User, error) {
 	array := ([]*User)(nil)
 	if err := m.Scan(&array); err != nil {
 		return nil, err
@@ -69,8 +78,10 @@ func (m *UserModel) All() ([]*User, error) {
 	return array, nil
 }
 
-func (m *UserModel) One() (*User, error) {
-	list, err := m.All()
+// First does the same logistics as One method from gdb.Model for model
+// as retuning first/one object with specified structure.
+func (m *UserModel) First() (*User, error) {
+	list, err := m.Select()
 	if err != nil {
 		return nil, err
 	}