Go by Example: Text 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” +which has the same API as “text/template” but has additional security features. +It should be used when generating HTML. + + |
+
+
+ +import ( + "log" + "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. + + |
+
+
+ + t1 := template.New("t1") ++ |
+
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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. + + |
+
+
+ + t1, err := t1.Parse("Value is {{.}}\n") + if err != nil { + log.Fatal(err) + } ++ |
+
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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. + + |
+
+
+ + t1 = template.Must(t1.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. + + |
+
+
+ + t1.Execute(os.Stdout, t1.Name()) + t1.Execute(os.Stdout, "some text") + t1.Execute(os.Stdout, true) + t1.Execute(os.Stdout, 5) + t1.Execute(os.Stdout, []string{ + "Go", + "Rust", + "C++", + "C#", + }) + t1.Execute(os.Stdout, struct{ name string }{ + name: "Jane Doe", + }) ++ |
+
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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. + + |
+
+
+ + t2, _ := template. + New("t2"). + Parse("Fullname: {{.Fullname}}\n") ++ |
+
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+
+ t2.Execute(os.Stdout, struct { + Fullname string + }{ + Fullname: "Jane Doe", + }) ++ |
+
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+ The same applies to maps; with maps there is no restriction on the case of key names. + + |
+
+
+ + t2.Execute(os.Stdout, map[string]string{ + "Fullname": "Mickey Mouse", + }) ++ |
+
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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. + + |
+
+
+ + t3, _ := template. + New("t3"). + Parse(`{{if .Field1}} + If block => {{.Field1}} + {{ else if .Field2}} + Else if block => {{.Field2}} + {{ else }} + Else block + {{ end }}`) ++ |
+
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+
+ s := struct { + Field1 string + Field2 []string + }{} ++ |
+
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+
+ s.Field1 = "" + s.Field2 = []string{} + t3.Execute(os.Stdout, s) ++ |
+
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+
+ s.Field1 = "Some text" + s.Field2 = nil + t3.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. + + |
+
+
+ + t4, _ := template. + New("t4"). + Parse(`Range: {{ range . }} + {{.}} + {{ end }}`) + t4.Execute(os.Stdout, + []string{ + "Go", + "Rust", + "C++", + "C#", + }) ++ |
+
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+ You can assign and reassign a value to a variable in templates. + + |
+
+
+ + t5, _ := template. + New("t5"). + Parse(`Variables: {{ $language := "go" }} + {{ $language }} + {{ $language = "C" }} + {{ $language }}`) + t5.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 {Jane Doe} +Fullname: Jane Doe +Fullname: Mickey Mouse+ |
+
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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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+
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+
+ C++
+ |
+
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+
+ C# +Variables: +go +C+ |
+
+ Next example: JSON. +
+ + + + +