Go by Example: Templates
+ +|
+ 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” +mostly used in web applications. +Here we show some of “text/template” features. + + |
+
+
+ +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. + + |
+
+
+ + 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. + + |
+
+
+ + 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. + + |
+
+
+ + 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. + + |
+
+
+ + 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. + + |
+
+
+ + 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. + + |
+
+
+ + 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. + + |
+
+
+ + 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. + + |
+
+
+ + t, _ = t.Parse(`Variables: {{ $language := "go" }} + {{ $language }} + {{ $language = "C" }} + {{ $language }}`) + t.Execute(os.Stdout, nil) +} ++ |
+
| + + | +
+
+ $ 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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+
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+ Else if block => Some text +Range: + Go+ |
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+
+ Rust
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+
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+ C++
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+
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+ C# +Variables: +go +C+ |
+
+ Next example: JSON. +
+ + + + +