How to Pass Functions to Go Templates?

Golang Templates: Passing Functions to Templates

Problem:

When attempting to pass a function to a template, the following error is encountered:

Error: template: struct.tpl:3: function "makeGoName" not defined

Solution:

To resolve this error, custom functions must be registered before parsing templates. Templates are designed for static analysis, requiring that the parser be able to distinguish valid function names from other identifiers.

Instead of using template.ParseFiles(), utilize the Template.ParseFiles() method, which is available after calling template.New(). This method registers functions before parsing the template.

Improved Code:

t, err := template.New("struct.tpl").Funcs(template.FuncMap{
    "makeGoName": makeGoName,
    "makeDBName": makeDBName,
}).ParseFiles("templates/struct.tpl")

Additionally, the Template.Execute() method returns an error. To observe any potential issues with output generation, handle this error:

if err := t.Execute(os.Stdout, data); err != nil {
    fmt.Println(err)
}

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