https://github.com/jr0senblum/jwalk

Helper module for working with Erlang proplists, eep 18, map and mochijson-style JSON representations
https://github.com/jr0senblum/jwalk

Last synced: about 1 month ago
JSON representation

Helper module for working with Erlang proplists, eep 18, map and mochijson-style JSON representations

• Host: GitHub
• URL: https://github.com/jr0senblum/jwalk
• Owner: jr0senblum
• License: other
• Created: 2015-11-20T19:08:23.000Z (about 9 years ago)
• Default Branch: master
• Last Pushed: 2019-11-24T18:18:35.000Z (about 5 years ago)
• Last Synced: 2024-10-10T16:06:29.546Z (2 months ago)
• Language: Erlang
• Homepage:
• Size: 2.96 MB
• Stars: 7
• Watchers: 2
• Forks: 1
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

        
jwalk  

=====

## Helper module for working with common Erlang representations of JSON: eep 18, map, 

mochijson-style, and proplists.

# 

[![Build Status](https://travis-ci.org/jr0senblum/jwalk.svg?branch=master)](https://travis-ci.org/jr0senblum/jwalk)

[![hex.pm version](https://img.shields.io/hexpm/v/jwalk.svg)](https://hex.pm/packages/jwalk)

# 

This work is inspired by [ej](https://github.com/seth/ej), but handles all common JSON 

representations: eep-18, map, mochijson-style and proplists, the types returned by 

[jsone](https://github.com/sile/jsone), [jiffy](https://github.com/davisp/jiffy), and 

[mochijson](https://github.com/mochi/mochiweb), for example. 

Anything good about this is probably due to the contributors and maintainers of ej, anything bad or 

awkward is completely my fault.

### Dependencies  

The source code is a single file, and there are no dependencies other than:

* Erlang 19.0 +

* Rebar3, for building

Hex package manager is used for package management.

### QuickStart  

#### clone

$ git clone git://github.com/jr0senblum/jwalk.git

$ cd jwalk

#### compile

$ make compile

#### run tests

$ make eunit

#### dialyze

$ make dialyze

#### Erlang shell

$ make start

    1> jwalk:get({"one"},#{<<"one">> => 1}).

    1

    2> jwalk:get({"one"},[{<<"one">>, 1}]).

    1

    3> jwalk:get({"one"},{[{<<"one">>, 1}]}).

    1

    4>  jwalk:get({"one"},{struct, [{<<"one">>, 1}]}).

    1

## Functions  

Jwalk functions always take at least two parameters: a first parameter which is a

tuple of elements representing a Path into a JSON Object, and a second 

parameter which is expected to be a valid JSON representation (map, proplist, etc.).

* ``jwalk:delete(Path, Object) -> Result`` 

 Removes the value at the location specified by Path from Object and returns a new structure 

* ``jwalk:get(Path, Object) -> Result | undefined``, 

 ``jwalk:get(Path, Object, Default) -> Result | Default``

 Returns the Value at the specificed Path from Object, or undefined or Default if not found  

* ``jwalk:set(Path, Object, Value) -> Result``

Sets a Value in Object at the specified Path and returns the new structure  

* ``jwalk:set_p(Path, Object, Value) -> Result``

Sets a Value in an Object at the specified Path creating intermediate nodes as necessary and 

returns the new structure

### Paths  

Paths into JSON Objects are expressed using a tuple of Path elements, a 

representation of a javascript-like path: i.e.,

``Obj.weapons.edged.distance``  becomes ``{"weapons","edged","distance"}``. 

Path elements representing JSON Member Names can be strings or binary, they 

will be internally converted to binary regardless.

In addition to the string/binary representations of Member Names, a Path element can 

be

* An integer index, or the atoms `first` and `last`, which will select 

an element out of a JSON Array.

* ``{select, {"name","value"|value}}`` which will select a subset of JSON objects 

from an Array that have a Member ``{"Name": "Value"|Value}`` 

* The atom `new`, used in conjunction with the functions set/2 and set_p/2, as the final element of a Path will add the supplied value to the stucture as the first element of an Array, the Array is created if necessary

Path, string elements can be binary or not, they will be converetd to binary regardless.

Examples follow.

### Usage Examples 

    Weapons = [{<<"edged">>, [[{<<"type">>, <<"swords">>}, {<<"distance">>, <<"medium">>}],   

                              [{<<"type">>, <<"bayonets">>},  {<<"distance">>, <<"medium">>}],

                              [{<<"type">>, <<"daggers">>}, {<<"distance">>, <<"close">>}]                            

                            ]                            

              }].

              

then

	

    1> jwalk:get({"edged", {select, {"distance","medium"}}},Weapons).

    [[{<<"type">>,<<"swords">>},{<<"distance">>,<<"medium">>}],

    [{<<"type">>,<<"bayonets">>},{<<"distance">>,<<"medium">>}]]

    2> jwalk:get({"edged",{select,{"distance","medium"}},1},Weapons).

    [{<<"type">>,<<"swords">>},{<<"distance">>,<<"medium">>}]

    3> jwalk:get({"edged",{select,{"distance","medium"}},1,"type"},Weapons).

    <<"swords">>

	

    % setting an element ...

    4> W2 = jwalk:set({"edged",3, "distance"}, Weapons, <<"very close">>).

    [{<<"edged">>,

     [[{<<"type">>,<<"swords">>},{<<"distance">>,<<"medium">>}],

      [{<<"type">>,<<"bayonets">>},{<<"distance">>,<<"medium">>}],

      [{<<"type">>,<<"daggers">>},{<<"distance">>,<<"very close">>}]]}]

    

    5> jwalk:get({"edged","distance"},W2).

    [<<"medium">>,<<"medium">>,<<"very close">>]

Given a map:

    Obj = #{<<"widget">> => 

            #{<<"debug">> => <<"on">>,

              <<"image">> => 

                  #{<<"alignment">> => <<"center">>,

                    <<"hOffset">> => 250,

                    <<"name">> => <<"sun1">>,

                    <<"src">> => <<"Images/Sun.png">>,

                    <<"vOffset">> => 250},

              <<"keys">> => [],

              <<"text">> => 

                  #{<<"alignment">> => <<"center">>,

                    <<"data">> => <<"Click Here">>,

                    <<"hOffset">> => 250,

                    <<"name">> => <<"text1">>,

                    <<"onMouseUp">> => <<"sun1.opacity = (sun1.opacity / 100) * 90;">>,

                    <<"size">> => 36,

                    <<"style">> => <<"bold">>,

                    <<"vOffset">> => 100},

              <<"values">> => [1,2,3,4,5],

              <<"version">> => <<"1">>,

              <<"window">> => 

                  #{<<"height">> => 500,

                    <<"name">> => <<"main_window">>,

                    <<"title">> => <<"Sample Konfabulator Widget">>,

                    <<"width">> => 500}}}.

then

    

    1> jwalk:get({"widget","debug"},Obj).

    <<"on">>

	

	2> jwalk:get({"widget","text"},Obj).

	#{<<"alignment">> => <<"center">>,

  	  <<"data">> => <<"Click Here">>,

  	  <<"hOffset">> => 250,

  	  <<"name">> => <<"text1">>,

  	  <<"onMouseUp">> => <<"sun1.opacity = (sun1.opacity / 100) * 90;">>,

  	  <<"size">> => 36,

  	  <<"style">> => <<"bold">>,

  	  <<"vOffset">> => 100}

      

set_p creates intermediary nodes: 

	1> jwalk:set_p({"users", {select, {"name", "sebastian"}}, "location"}, #{}, <<"Germany">>).

    #{<<"users">> => [#{<<"location">> => <<"Germany">>,<<"name">> => <<"sebastian">>}]}

	2> jwalk:set_p({"users", {select, {"name", "sebastian"}}, "location"}, [{}],    <<"Germany">>).

	[{<<"users">>,

	  [[{<<"name">>,<<"sebastian">>},

            {<<"location">>,<<"Germany">>}]]}]

    3> jwalk:set_p({"users", {select, {"name", "sebastian"}}, "location"}, {[]},    <<"Germany">>).

	{[{<<"users">>,

   	  [{[{<<"name">>,<<"sebastian">>},

             {<<"location">>,<<"Germany">>}]}]}]}

    4> jwalk:set_p({"users", {select, {"name", "sebastian"}}, "location"}, {struct,[]}, <<"Germany">>).

    {struct,[{<<"users">>,

        [{struct,[{<<"name">>,<<"sebastian">>},

                  {<<"location">>,<<"Germany">>}]}]}]}