JPJson

Json is an alternative to XML. It is a human-readable text format to transmit data objects consisting of attribute–value pairs. It is used primarily to transmit data to/from a server.

The Json format has several advantages over XML:

• It is easier to read as it is not based on tags.
• More compact than XML, resulting on less network consumption to transmit the same data.
• Clever structure based on arrays, maps and standard types (number, boolean, string, null)

Have a look to an XML structure:

<xml>
    <name>John</name>
    <id>82</id>
    <rank>3</rank>
    <score>32410</score>
    <rank>3</rank>
    <friends_id>
        <id>119</id>
        <id>384</id>
        <id>42</id>
        <id>746</id>
    </friends_id>
    <location>
        <city>New York</city>
        <country>US</country>
    </location>
</xml>

Now, look at the equivalent Json structure, with the same data:

{
    "name":"John",
    "id":82,
    "rank":3,
    "score":32410,
    "rank":3,
    "friends_id":[119,384,42,746],
    "location":{
        "city":"New York",
        "country":"US"
    }
}

The Json is roughly 40% lighter and easier to read because it is consisting of attribute–value pairs while XML is based on tags.

JPJson offers 2 ways to create a Json object:

• From a Json string: jJson = JPJson.createFromString ( sJson )
• From a Json you have downloaded: JPJson.receive ( sTag, sURI ) and jJson = JPJson.getFromTag ( sTag )

Now if you want to get the name of the player or its score, it's really easy, look:

local sName = jJson["name"]
local nScore = jJson["score"]

Accessing a sub-element is also a piece of cake:

local sCountry = jJson["location"]["country"]

This was for accessing values contained in maps (or objects as it is commonly named in Json). Here is how to browse an array (defined with square brackets):

for i = 0, JPJson.getSize ( jJson["friends_id"] ) - 1 do
    local nFriendId = jJson["friends_id"][i]
    --Your code here

end

It is really easy, no need to use the API for browsing the Json element, you can access it directly with keys and indexes!