Tcllib JSON

The Tcllib JSON module provides a parser and a generator. The parser is in the namespace ::json, the generator is in the namespace ::json::write. Both form an "ensemble command".

Reference

json

json::write

Parse JSON

json2prettydict Patch

ABU 2012-04-18:

Few weeks ago I posted a patch-proposal [L1 ] for the json package.

I added a new proc named json2prettydict. Aim of this proc is to return a "pretty-printed" tcl-dictionary

I think this proc could be useful for documenting complex nested dictionaries.

Here is an example:

set jsonStr { \
  { "photos": { "page": 1, "pages": "726", "perpage": 3, "total": "7257", 
    "photo": [
      { "id": "6974156079", "owner": "74957296@N08", "secret": "005d743f82", "server": "7197", "farm": 8, "title": "Kenya Watamu \"Deep Sea Fishing\" \"Indian Ocean\" \"Blue Marlin\"", "ispublic": 1, "isfriend": 0, "isfamily": 0 },
      { "id": "6822988100", "owner": "52857411@N08", "secret": "56630c18e8", "server": "7183", "farm": 8, "title": "Gedi Ruins, Local Guide", "ispublic": 1, "isfriend": 0, "isfamily": 0 },
      { "id": "6822909640", "owner": "52857411@N08", "secret": "f4e392ea36", "server": "7063", "farm": 8, "title": "Local Fisherman, Mida Creek", "ispublic": 1, "isfriend": 0, "isfamily": 0 }
    ] }, "stat": "ok" }
}

First, just for comparision, call json2dict

set d1 [json::json2dict $jsonStr]

result is the following

photos {page 1 pages 726 perpage 3 total 7257 photo {{id 6974156079 owner 74957296@N08 secret 005d743f82 server 7197 farm 8 title {Kenya Watamu "Deep Sea Fishing" "Indian Ocean" "Blue Marlin"} ispublic 1 isfriend 0 isfamily 0} {id 6822988100 owner 52857411@N08 secret 56630c18e8 server 7183 farm 8 title {Gedi Ruins, Local Guide} ispublic 1 isfriend 0 isfamily 0} {id 6822909640 owner 52857411@N08 secret f4e392ea36 server 7063 farm 8 title {Local Fisherman, Mida Creek} ispublic 1 isfriend 0 isfamily 0}}} stat ok

then create a pretty printed dictionary

set d2 [json::json2prettydict $jsonStr]

result is still a valid tcl-dict, just more readable

photos {
    page 1
    pages 726
    perpage 3
    total 7257
    photo {
        {
            id 6974156079
            owner 74957296@N08
            secret 005d743f82
            server 7197
            farm 8
            title {Kenya Watamu "Deep Sea Fishing" "Indian Ocean" "Blue Marlin"}
            ispublic 1
            isfriend 0
            isfamily 0
        }
        {
            id 6822988100
            owner 52857411@N08
            secret 56630c18e8
            server 7183
            farm 8
            title {Gedi Ruins, Local Guide}
            ispublic 1
            isfriend 0
            isfamily 0
        }
        {
            id 6822909640
            owner 52857411@N08
            secret f4e392ea36
            server 7063
            farm 8
            title {Local Fisherman, Mida Creek}
            ispublic 1
            isfriend 0
            isfamily 0
        }
    }

}
stat ok

EF For an experiment on how to access data from the "parsed tree" (which really are dictionaries), see Playing XPath with JSON.

Write JSON

Convert a dictionary into a JSON object

DcK 2017-10-16 To communicate with a REST API, I need to send a JSON payload, initially available in TCL code as a dictionary.

The ::json::write object nicely solves this problem, but expects the values already to be valid JSON data. So if you accept the paradigm "everything is a string", and want to encode everything as a string, you can use:

proc dict2json {dictToEncode} {
    ::json::write object {*}[dict map {k v} $dictToEncode {
        set v [::json::write string $v]
    }]
}

To go beyond the "all values are strings" paradigm, the map script code has to write something else according your rules.

Performance

dbohdan 2015-03-23: Tcllib JSON gets a significant speed boost from jsonc if you have tcllibc and critcl installed.

Change Log

JH 2006-08-17: I have made the JSON parser functional and moved it into tcllib (see https://core.tcl-lang.org/tcllib/dir?name=modules/json/ ). I started with what CMcC had here, but rewrote it for correctness and improved speed.

JSON	Category tcllib