json_fill()

json_fill(<json>, <pointer>, <value>[, <pointer>, <value>, ...])

Returns <json> with the value at each <pointer> replaced by its <value>. <json> is a template: usually JSON stored in an attribute and read with v() or get(), so a large structure such as a portal form is written once instead of being rebuilt from many json() calls every time it is used.

A <pointer> is a JSON Pointer: each step starts with /, an object member by its name and an array element by its number counted from 0. /pages/0/title is the title of the first element of pages. A / inside a member name is written ~1, and a ~ is written ~0. An empty pointer names the whole template. The pointer must name a value the template already has; json_fill() changes values, it does not add them.

What the template holds at a pointer decides how <value> is read:

string any text, written as a JSON string with quotes and escapes added
number a number
true or false “true”, “1”, “false” or “0”
object, array or null valid JSON, for instance from json() or json_array()

Values are plain text: colour and markup are removed. If the template is not valid JSON, or a pointer or value is wrong, json_fill() returns an error starting with #-1 that names the pointer.

::: seealso

Fill examples

> &schema me={"title":"","pages":[{"title":"","order":0}],"open":false}
> think json_fill(v(schema),/title,Hello %n,/pages/0/title,First,/pages/0/order,1,/open,1)
{"title":"Hello Bob","pages":[{"title":"First","order":1}],"open":true}

> think json_fill(v(schema),/pages/0/order,soon)
#-1 VALUE FOR /pages/0/order MUST BE A NUMBER