golang template nested loop

Nested loops in Go templates allow you to iterate over multiple levels of data structures. Here is an explanation of each step involved in using nested loops in Go templates:

  1. Define the template: Start by defining the template using the template.New function and providing a name for the template. For example, you can use tmpl := template.New("mytemplate").

  2. Parse the template: Use the Parse or ParseFiles function to parse the template string or read it from a file, respectively. This step converts the template string into an internal representation that can be executed later. For example, you can use tmpl.Parse("{{range .Items}}...{{end}}") to parse a template string.

  3. Execute the template: To execute the template, you need to provide the template with the data it needs. You can use the Execute or ExecuteTemplate method of the template object to execute the template. For example, you can use tmpl.Execute(os.Stdout, data) to execute the template and write the output to the standard output.

  4. Iterate over nested data: To create a nested loop, use the range action in the template. The range action allows you to iterate over a data structure, such as an array or a slice. For example, you can use {{range .Items}}...{{end}} to iterate over the Items field of the data structure.

  5. Access nested values: Within the nested loop, you can access the values of the nested data structure using the dot notation. For example, if Items is a slice of structs and each struct has a field called Name, you can access it using {{.Name}}.

  6. Nest additional loops: To create a nested loop, you can simply use another range action within the existing loop. This allows you to iterate over nested data structures. For example, you can use {{range .Items}}{{range .SubItems}}...{{end}}{{end}} to iterate over both Items and SubItems.

  7. Use control structures: Go templates also provide control structures like if, else, and range with an else clause. These control structures allow you to conditionally render content or iterate over specific elements. For example, you can use {{if .Condition}}...{{else}}...{{end}} to conditionally render content based on a condition.

  8. Output the result: Finally, the executed template will produce output that can be written to a writer, such as the standard output or a file. Use the appropriate method, such as Execute or ExecuteTemplate, to write the output to the desired writer.

By following these steps, you can effectively use nested loops in Go templates to iterate over and render complex data structures.