--- /dev/null
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package template_test
+
+import (
+ "io"
+ "io/ioutil"
+ "log"
+ "os"
+ "path/filepath"
+ "text/template"
+)
+
+// templateFile defines the contents of a template to be stored in a file, for testing.
+type templateFile struct {
+ name string
+ contents string
+}
+
+func createTestDir(files []templateFile) string {
+ dir, err := ioutil.TempDir("", "template")
+ if err != nil {
+ log.Fatal(err)
+ }
+ for _, file := range files {
+ f, err := os.Create(filepath.Join(dir, file.name))
+ if err != nil {
+ log.Fatal(err)
+ }
+ defer f.Close()
+ _, err = io.WriteString(f, file.contents)
+ if err != nil {
+ log.Fatal(err)
+ }
+ }
+ return dir
+}
+
+// Here we demonstrate loading a set of templates from a directory.
+func ExampleTemplate_glob() {
+ // Here we create a temporary directory and populate it with our sample
+ // template definition files; usually the template files would already
+ // exist in some location known to the program.
+ dir := createTestDir([]templateFile{
+ // T0.tmpl is a plain template file that just invokes T1.
+ {"T0.tmpl", `T0 invokes T1: ({{template "T1"}})`},
+ // T1.tmpl defines a template, T1 that invokes T2.
+ {"T1.tmpl", `{{define "T1"}}T1 invokes T2: ({{template "T2"}}){{end}}`},
+ // T2.tmpl defines a template T2.
+ {"T2.tmpl", `{{define "T2"}}This is T2{{end}}`},
+ })
+ // Clean up after the test; another quirk of running as an example.
+ defer os.RemoveAll(dir)
+
+ // pattern is the glob pattern used to find all the template files.
+ pattern := filepath.Join(dir, "*.tmpl")
+
+ // Here starts the example proper.
+ // T0.tmpl is the first name matched, so it becomes the starting template,
+ // the value returned by ParseGlob.
+ tmpl := template.Must(template.ParseGlob(pattern))
+
+ err := tmpl.Execute(os.Stdout, nil)
+ if err != nil {
+ log.Fatalf("template execution: %s", err)
+ }
+ // Output:
+ // T0 invokes T1: (T1 invokes T2: (This is T2))
+}
+
+// This example demonstrates one way to share some templates
+// and use them in different contexts. In this variant we add multiple driver
+// templates by hand to an existing bundle of templates.
+func ExampleTemplate_helpers() {
+ // Here we create a temporary directory and populate it with our sample
+ // template definition files; usually the template files would already
+ // exist in some location known to the program.
+ dir := createTestDir([]templateFile{
+ // T1.tmpl defines a template, T1 that invokes T2.
+ {"T1.tmpl", `{{define "T1"}}T1 invokes T2: ({{template "T2"}}){{end}}`},
+ // T2.tmpl defines a template T2.
+ {"T2.tmpl", `{{define "T2"}}This is T2{{end}}`},
+ })
+ // Clean up after the test; another quirk of running as an example.
+ defer os.RemoveAll(dir)
+
+ // pattern is the glob pattern used to find all the template files.
+ pattern := filepath.Join(dir, "*.tmpl")
+
+ // Here starts the example proper.
+ // Load the helpers.
+ templates := template.Must(template.ParseGlob(pattern))
+ // Add one driver template to the bunch; we do this with an explicit template definition.
+ _, err := templates.Parse("{{define `driver1`}}Driver 1 calls T1: ({{template `T1`}})\n{{end}}")
+ if err != nil {
+ log.Fatal("parsing driver1: ", err)
+ }
+ // Add another driver template.
+ _, err = templates.Parse("{{define `driver2`}}Driver 2 calls T2: ({{template `T2`}})\n{{end}}")
+ if err != nil {
+ log.Fatal("parsing driver2: ", err)
+ }
+ // We load all the templates before execution. This package does not require
+ // that behavior but html/template's escaping does, so it's a good habit.
+ err = templates.ExecuteTemplate(os.Stdout, "driver1", nil)
+ if err != nil {
+ log.Fatalf("driver1 execution: %s", err)
+ }
+ err = templates.ExecuteTemplate(os.Stdout, "driver2", nil)
+ if err != nil {
+ log.Fatalf("driver2 execution: %s", err)
+ }
+ // Output:
+ // Driver 1 calls T1: (T1 invokes T2: (This is T2))
+ // Driver 2 calls T2: (This is T2)
+}
+
+// This example demonstrates how to use one group of driver
+// templates with distinct sets of helper templates.
+func ExampleTemplate_share() {
+ // Here we create a temporary directory and populate it with our sample
+ // template definition files; usually the template files would already
+ // exist in some location known to the program.
+ dir := createTestDir([]templateFile{
+ // T0.tmpl is a plain template file that just invokes T1.
+ {"T0.tmpl", "T0 ({{.}} version) invokes T1: ({{template `T1`}})\n"},
+ // T1.tmpl defines a template, T1 that invokes T2. Note T2 is not defined
+ {"T1.tmpl", `{{define "T1"}}T1 invokes T2: ({{template "T2"}}){{end}}`},
+ })
+ // Clean up after the test; another quirk of running as an example.
+ defer os.RemoveAll(dir)
+
+ // pattern is the glob pattern used to find all the template files.
+ pattern := filepath.Join(dir, "*.tmpl")
+
+ // Here starts the example proper.
+ // Load the drivers.
+ drivers := template.Must(template.ParseGlob(pattern))
+
+ // We must define an implementation of the T2 template. First we clone
+ // the drivers, then add a definition of T2 to the template name space.
+
+ // 1. Clone the helper set to create a new name space from which to run them.
+ first, err := drivers.Clone()
+ if err != nil {
+ log.Fatal("cloning helpers: ", err)
+ }
+ // 2. Define T2, version A, and parse it.
+ _, err = first.Parse("{{define `T2`}}T2, version A{{end}}")
+ if err != nil {
+ log.Fatal("parsing T2: ", err)
+ }
+
+ // Now repeat the whole thing, using a different version of T2.
+ // 1. Clone the drivers.
+ second, err := drivers.Clone()
+ if err != nil {
+ log.Fatal("cloning drivers: ", err)
+ }
+ // 2. Define T2, version B, and parse it.
+ _, err = second.Parse("{{define `T2`}}T2, version B{{end}}")
+ if err != nil {
+ log.Fatal("parsing T2: ", err)
+ }
+
+ // Execute the templates in the reverse order to verify the
+ // first is unaffected by the second.
+ err = second.ExecuteTemplate(os.Stdout, "T0.tmpl", "second")
+ if err != nil {
+ log.Fatalf("second execution: %s", err)
+ }
+ err = first.ExecuteTemplate(os.Stdout, "T0.tmpl", "first")
+ if err != nil {
+ log.Fatalf("first: execution: %s", err)
+ }
+
+ // Output:
+ // T0 (second version) invokes T1: (T1 invokes T2: (T2, version B))
+ // T0 (first version) invokes T1: (T1 invokes T2: (T2, version A))
+}