Go by Example: Templates
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- Go offers built-in support for creating -dynamic content or showing customized output to the user called Template. - - |
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- package main -- |
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- Go has two template packages. one is “text/template” for -regular text manipulation, and another one is “html/template”. -“html/template” has the same API as text/template which has additional security features. -It should be used when generating HTML -Here we show some of “text/template” features. - - |
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- -import ( - "os" - "text/template" -) -- |
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- func main() { -- |
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- New creates a template with a specific name and returns a pointer to it. - - |
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- - t := template.New("my-template") -- |
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- Parse parses its parameter as template body. -We use {{.}} to access the value passed to the template when it’s getting executed. - - |
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- - t, _ = t.Parse("Value is {{.}}\n") -- |
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- If we want to ignore the errors we can use Must function. -It will panic if an error occurs when parsing the template. - - |
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- - t = template.Must(t.Parse("Value is {{.}}\n")) -- |
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- Execute applies parsed template to the data we pass to it and writes the output to the io.Writer. - - |
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- - t.Execute(os.Stdout, t.Name()) - t.Execute(os.Stdout, "some text") - t.Execute(os.Stdout, true) - t.Execute(os.Stdout, 5) - t.Execute(os.Stdout, []string{ - "Go", - "Rust", - "C++", - "C#", - }) - t.Execute(os.Stdout, struct{ name string }{ - name: "Arash", - }) -- |
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- If the data is a struct we can use the {{.FieldName}} action to access its fields. -The fields should be exported to be accessible when template is executing. - - |
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- - t, _ = t.Parse("Firstname: {{.Firstname}}" + - ", Lastname: {{.Lastname}}\n") -- |
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- t.Execute(os.Stdout, struct { - Firstname, Lastname string - }{ - Firstname: "Arash", - Lastname: "Sameni", - }) -- |
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- Samething applies for maps. But it’s not necessary to have uppercase fields. - - |
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- - t.Execute(os.Stdout, map[string]string{ - "Firstname": "Robert", - "Lastname": "Griesemer", - }) -- |
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- You can use if control structure to show data conditionally. -The data between if block will be shown if the field is truthy. -Means it is not false boolean, empty string, nil or zero length slice, nil map/pointer. - - |
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- - t, _ = t.Parse(`{{if .Field1}} - If block => {{.Field1}} - {{ else if .Field2}} - Else if block => {{.Field2}} - {{ else }} - Else block - {{ end }}`) -- |
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- s := struct { - Field1, Field2 interface{} - }{} -- |
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- s.Field1 = "" - s.Field2 = []string{} - t.Execute(os.Stdout, s) -- |
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- s.Field1 = nil - s.Field2 = "Some text" - t.Execute(os.Stdout, s) -- |
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- Using a range action you can loop through a slice. -Each time the range block is getting executed dot will be set -to current item of slice. -You can use $ in blocks to access outside data. - - |
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- - t, _ = t.Parse(`Range: {{ range . }} - {{.}} - {{ end }}`) - t.Execute(os.Stdout, []string{ - "Go", - "Rust", - "C++", - "C#", - }) -- |
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- You can assign and reassign a value to a variable in templates. - - |
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- - t, _ = t.Parse(`Variables: {{ $language := "go" }} - {{ $language }} - {{ $language = "C" }} - {{ $language }}`) - t.Execute(os.Stdout, nil) -} -- |
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- $ go run templates.go -Value is my-template -Value is some text -Value is true -Value is 5 -Value is [Go Rust C++ C#] -Value is {Arash} -Firstname: Arash, Lastname: Sameni -Firstname: Robert, Lastname: Griesemer- |
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- Else block
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- Else if block => Some text -Range: - Go- |
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- Rust
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- C++
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- C# -Variables: -go -C- |
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- Next example: JSON. -
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