Go: gin && xorm && reflect && strconv && …

Go: list

• gin
• xorm
• net/http
• reflect
• strconv
• validator
• swagger

gin

Framwork

Gin is a web framework written in Go (Golang). It features a martini-like API with much better performance, up to 40 times faster thanks to httprouter. If you need performance and good productivity, you will love Gin

• Custom Middleware

  • list of external middleware

• 實作心得區

  • 只要 gin.Content set statusCode 204, response body 就會空空喔～～～～～

• binding tag

  • 用 shouldBindWithxxx…
    • 在 model tag 中 加入 binding:"required" 等 會幫你檢查
    • 格式不對 或沒有填必填欄位的時候 會出 err
  • 後端(DB, Modle)如果吃 int 的話，前端要塞 number type，空值的話就 null

xorm

• engine.count(): Count records

   counts, err := engine.Count(&user)
   // SELECT count(*) AS total FROM user
     
   counts, err := engine.SQL("select count(*) FROM user").Count()
   // select count(*) FROM user
  

• name mapping rule

  • use xorm.IMapper interface to implement. There are two IMapper implemented: SnakeMapper and SameMapper.
    • SnakeMapper means struct name is word by word and table name or column name as _.
    • SameMapper means same name between struct and table.

  • SnakeMapper example:

    • sql:

                  
          CREATE TABLE product_order (
              id primary key,
              create_time timestamp,
              update_time timestamp,
              User_name varchar(50),
              ...
          )
      

    • go:

                  
          import "time"
      
          type ProductOrder struct {
              Id string `xorm:"pk"`
              CreateTime time.Time `xorm:timestamp utc`
              UpdateTime time.Time `xorm:timestamp utc`
              UserName string `xorm:"varchar(50)"`
              ...
          }
      

  • 自動 generate time (app server time)

    • type GenerateTime struct {
         UpdateTime time.Time `xorm:"created" json:"update_time"`
          CreateTime time.Time `xorm:"created" json:"create_time"`
      }
      

• types:

  • column types

• ORM_Methods

• xorm.io: struct tag method

  • If field is name of Id and type of int64, xorm makes it as auto increment primary key. If another field, use struct tag xorm:”pk”.

• Omitempty:

  • 在 struct tag 加上 binding:"omitempty" 在 type 的地方加 *

    • 預設數值才會是 null

    • ex: name *string xorm:"varchar" json:"name" bindgin:"omitempty"

net/http

• status code

reflect

• https://golang.org/pkg/reflect/

  • Package reflect implements run-time reflection, allowing a program to manipulate objects with arbitrary types. The typical use is to take a value with static type interface{} and extract its dynamic type information by calling TypeOf, which returns a Type.

  • A call to ValueOf returns a Value representing the run-time data. Zero takes a Type and returns a Value representing a zero value for that type.

• https://blog.golang.org/laws-of-reflection

  • Reflection in computing is the ability of a program to examine its own structure, particularly through types; it’s a form of metaprogramming. It’s also a great source of confusion.

  • In this article we attempt to clarify things by explaining how reflection works in Go. Each language’s reflection model is different (and many languages don’t support it at all), but this article is about Go, so for the rest of this article the word “reflection” should be taken to mean “reflection in Go”.

• Elem

  • return a type’s element type
  • It panics if the type’s Kind is not Array, Chan, Map, Ptr, or Slice.

strconv

Package strconv implements conversions to and form string represntations of basic dataa types.

• Most Common Conversions

  • Atoi
    • string to int
  • Itoa
    • int to string

Go: pointers

• 好棒棒網站

package main

import "fmt"

func main() {
	i, j := 42, 2701

	p := &i         // point to i
	fmt.Println(*p) // read i through the pointer
	*p = 21         // set i through the pointer
	fmt.Println(i)  // see the new value of i

	p = &j         // point to j
	*p = *p / 37   // divide j through the pointer
	fmt.Println(j) // see the new value of j
}

validate

• Package validator implements value validations for structs and individual fields based on tags.

Swagger

• swagger install && init ~

  • go get -u github.com/swaggo/swag/cmd/swag

  • swag init 我 mac cmd 不會自動幫我抓 Windows 會唷～

    • 所以我都直接 XDDD
      • EX: /Users/yutingwu/go/bin/swag init

• annotation info

  • host 不加會自動抓 resource domain