Go To-Do list

# Go Template Walkthrough Guide ## Concepts & Syntax They’re delimited by `{{ }}`. Other, other non-delimited parts are left untouched. ### Data evaluations To obtain data from a struct, you can use the `{{ .FieldName}}` action, which will replace it with the `FieldName` value of the given struct, on parse time. The struct is given to the `Execute` function, which we’ll cover later. There’s also the `{{.}}` action that you can use to refer to a value of non-struct types. ### Conditions `if`,`else if`,`end` structure is supported. For example: ``` {{if .FieldName}} Value of FieldName is {{ .FieldName }} {{end}} Or {{if .FieldName}} action {{ else }} action 2 {{end}} ``` ### Loops Using the `range` action you can loop through a slice. A `range` actions is defined using the `{{range .Member}} ... {{end}}` template. If your slice is a non-struct type, you can refer to the value using the `{{ . }}` action. In case of structs, you can refer to the value using the `{{ .Member }}` action, as already explained. ### Functions, Pipelines and Variables Actions have several built-in functions that are used along with pipelines to additionally parse output. Pipelines are annotated with `|` and the default behavior is sending data from the left side to the function to the right side. Functions are used to escape the action’s result. There’re several functions available by default such as, `html` which returns HTML escaped output, safe against code injection or `js` which returns JavaScript escaped output. Using the `with` action, you can define variables that are available in that `with` block: `{{ with $x := <^>result-of-some-action<^> }} {{ $x }} {{ end }}`. ## Parsing Templates The three most important and most frequently used functions are: * `New` — allocates new, undefined template, * `Parse` — parses given template string and return parsed template, * `Execute` — applies parsed template to the data structure and writes result to the given writer. Let's run through a sample: ``` $ mkdir go-template && cd go-template $ cat > main.go < todo.tpl < Go To-Do list

To-Do list for user: {{ .User }}

Task	Done
{{ .Name }}	{{ if .Done }}Yes{{ else }}No{{ end }}

EOF $ cat > html.go < Note: In line 67 above, if we use an ad-hoc template name say `html-template` , we would get error: `panic: template: "html-template" is an incomplete or empty template` > > ``` > t, err := template.New("html-template").ParseFiles(paths...) > ``` > > So the template name MUST be the FIRST FILE NAME if there are many template files. How if we have multiple template files? We need to `define` the template names: ``` $ cat > todo.tpl < Go To-Do list 1

To-Do list for user: {{ .User }}

Task	Done
{{ .Name }}	{{ if .Done }}Yes{{ else }}No{{ end }}

{{ end }} EOF $ cat > todo2.tpl < Go To-Do list 2

To-Do list for user: {{ .User }}

Task	Done
{{ .Name }}	{{ if .Done }}Yes{{ else }}No{{ end }}

{{ end }} EOF $ cat > html.go < todo.tpl < Go To-Do list 1

To-Do list for user: {{ .User }}

Task	Done
{{ .Name }}	{{ if .Done }}Yes{{ else }}No{{ end }}

{{ template "todo2" . }} {{ end }} EOF ``` Please note this line: `{{ template "todo2" . }}` ## References {% embed url="" %} {% embed url="" %}