code review 5694100: text/template: add example showing use of custom function

src/pkg/text/template/examplefunc_test.go

+// 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 (
+        "log"
+        "os"
+        "strings"
+        "text/template"
+)
+
+// This example demonstrates a custom function to process template text.
+// It installs the strings.Title function and uses it to
+// Make Title Text Look Good In Our Template;s Output.

[adg, 2012/02/28 04:28:14]

s/;/'/

+func ExampleTemplate_func() {
+        // First we create a FuncMap with which to register the function.

[adg, 2012/02/28 04:28:14]

Maybe say that this is where we give it the name "title", which we use to refer
to this function inside templates.

+        funcMap := template.FuncMap{
+                "title": strings.Title,
+        }
+
+        // A simple template definition to test our function.
+        // We print the input text several ways:
+        // - the original
+        // - title-cased
+        // - title-cased and then printed with %q
+        // - printed with %q and then title-cased.
+        templateText := "Input: {{printf `%q` .}};\n"

[adg, 2012/02/28 04:28:14]

const templateText = `
...
` ?

+        templateText += "Output 0: {{title .}}\n"
+        templateText += "Output 1: {{title . | printf `%q`}}\n"
+        templateText += "Output 2: {{printf `%q` . | title}}"
+
+        // Create a template, add the function map, and parse the text.
+        tmpl, err := template.New("titleTest").Funcs(funcMap).Parse(templateText)
+        if err != nil {
+                log.Fatalf("template parsing: %s", err)
+        }
+
+        // Run the template to verify the output.
+        err = tmpl.Execute(os.Stdout, "the go programming language")
+
+        // Output:
+        // Input: "the go programming language";
+        // Output 0: The Go Programming Language
+        // Output 1: "The Go Programming Language"
+        // Output 2: "The Go Programming Language"
+}