Associative array/Iteration: Difference between revisions

'''Language:'''

'''Standard library templates:'''

In addition to the for/range features of the language, the text/template and html/template packages of the standard library have map iteration features. Some differences worth noting:

* A single assigned value in a template is the map value. With the language for/range it is the key.

* Templates have no equivalent of _; a dummy variable must be used.

* In a template, if map keys are a comparable basic type, then iteration proceeds in key order. With the language for/range, iteration is in non-deterministic order.

<lang go>package main

import (

"os"

"text/template"

)

func main() {

m := map[string]int{

"hello": 13,

"world": 31,

"!": 71,

}

// iterating over key-value pairs:

template.Must(template.New("").Parse(`

{{- range $k, $v := . -}}

key = {{$k}}, value = {{$v}}

{{end -}}

`)).Execute(os.Stdout, m)

// iterating over keys:

template.Must(template.New("").Parse(`

{{- range $k, $v := . -}}

key = {{$k}}

{{end -}}

`)).Execute(os.Stdout, m)

// iterating over values:

template.Must(template.New("").Parse(`

{{- range . -}}

value = {{.}}

{{end -}}

`)).Execute(os.Stdout, m)

}</lang>

{{out}}

Note order by key.

<pre>

key = !, value = 71

key = hello, value = 13

key = world, value = 31

key = !

key = hello

key = world

value = 71

value = 13

value = 31

</pre>