with

The template command {{with _expression_}} sets the context to the result of expression and executes the enclosed expressions or executes the corresponding {{else}} block if the expression evaluates to null.

Input:

{
  "user": {
    "name": "alice",
  }
}

Template:

<template>
{
  {{with ./user}}
    "Name": {{ name }}
  {{else}}
    "Name": "unknown"
  {{end}}
}
</template>

Output:

{
  "Name": "alice"
}

Example: with and json-doc()

{{with}} is especially useful in conjunction with json-doc() to consolidate data from multiple sources using more compact expressions.

Input:

{
  "location": "home"
}

Input fit://request/request/body:

{
  "user": "fred",
  "pass": "wilma"
}

Template:

<template>
{
  "realm": {{ location }},
  {{with json-doc("fit://request/request/body") }}
    "user": {{ user }},
    "password": {{ pass }}
  {{end}}
}
</template>

Output:

{
  "realm": "home",
  "user": "wilma",
  "password": "fred"
}