[Golang] Template(一)

html/template/ package實作用來生成HTML的data-driven templates, 並且可以防止code injection。

html/template提供跟 text/template 相同介面, 不管是不是輸出HTML建議都用這個html/template package。

以下內容部份整理與翻譯自官網http/template, 以及 Go Template Primer。

使用樣板

例如, 要發給參加婚宴賓客的回覆(出處):

package main
import (
  "html/template"
  "os"
)
const letter = `
Dear {{.Name}},
{{if .Attended}}
It was a pleasure to see you at the wedding.{{else}}
It is a shame you couldn't make it to the wedding.{{end}}
{{with .Gift}}
Thank you for the lovely {{.}}.
{{end}}
Best wishes,
Josie
`

//Prepare some data to insert into template
type Recipient struct {
  Name, Gift string
  Attended   bool
}

func main() {
  recipients := []Recipient{
    {"Aunt Mildred", "bone china tea set", true},
    {"Uncle John", "moleskin pants", false},
    {"Cousin Rodney", "", false},
  }
  //Create a new template and parse the letter into it.
  t := template.Must(template.New("letter").Parse(letter))
  //Execute the template for each recipient
  for _, r := range recipients {
    err := t.Execute(os.Stdout, r)
    if err != nil {
      panic(err)
    } 
  }
}

輸出結果:

Dear Aunt Mildred,

It was a pleasure to see you at the wedding.
Thank you for the lovely bone china tea set.

Best wishes,
Josie

Dear Uncle John,

It is a shame you couldn't make it to the wedding.
Thank you for the lovely moleskin pants.

Best wishes,
Josie

Dear Cousin Rodney,

It is a shame you couldn't make it to the wedding.

Best wishes,
Josie

上述例子步驟分述如下。

產生樣板字串

用來生成樣板用的:

const letter = `
Dear {{.Name}},
{{if .Attended}}
It was a pleasure to see you at the wedding.{{else}}
It is a shame you couldn't make it to the wedding.{{end}}
{{with .Gift}}
Thank you for the lovely {{.}}.
{{end}}
Best wishes,
Josie
`

有用過樣板引擎的朋友應該都會很快就能適應(語法參考)

變數和函式都用{{}}。

注意使用Actions像是{{if}}等述句單獨放一行的話,就會獨占一行空間。

要塞入樣板的資料結構(struct)

Go的樣板只接受struct資料餵入:

type Recipient struct {
  Name, Gift string
  Attended   bool
}

準備我們要塞入的資料

recipients := []Recipient{
  {"Aunt Mildred", "bone china tea set", true},
  {"Uncle John", "moleskin pants", false},
  {"Cousin Rodney", "", false},
}

產生樣板

利用樣板字串產生一個樣板,並且幫這個樣板取名字

t := template.Must(template.New("letter").Parse(letter))

如果樣板字串是來自於外部檔案, 那麼就利用template.ParseFiles():

t := template.Must(template.ParseFiles("tmpl/Letter.html"))

套用樣板

將準備好的資料套用樣板, 輸出最後結果

for _, r := range recipients {
  err := t.Execute(os.Stdout, r)
  if err != nil {
    panic(err)
  } 
}

樣板語法 -- iteration

跟Go一樣, 用超多range來遍歷各個資料結構像是map, array或是slice,

using context:

{{ range array }}
  {{ . }}
{{ end }}

或是宣告變數名稱:

{{range $element := array}}
  {{ $element }}
{{ end }}

多宣告index:

{{range $index, $element := array}}
  {{ $index }}
  {{ $element }}
{{ end }}

More

go template excute template include html

Go Template Primer

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