JSON Object

These are examples for using the JSON object in Lua to encode/decode and read and write JSON files.

Methods

Refer to the RapidJSON topic in Q-SYS Help for a list of methods and their descriptions.

Text Controller Setup

Drag in a Text Controller and name it JSON Encode/Decode. Add a Combo Box named Type, three Text Boxes named Input, Name and Version, and a Text Indicator named Output (see screenshot).

Next, copy the Example Code to the Text Controller.

JSON Encode/Decode Example Code

Copy

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-- Include
rapidjson = require("rapidjson")  -- include the rapidjson library


-- Aliases
Name = Controls.Name
Version = Controls.Version
Type = Controls.Type
Input = Controls.Input
Output = Controls.Output


-- Constants
JSONChoices = {"Encode","Decode"}  -- combobox choices


-- Functions
function ShowJSONVersion()  -- gets and prints JSON version to text boxes
  Name.String = rapidjson._NAME  -- get rapidjson name
  Version.String = rapidjson._VERSION  -- get rapidjson version
end

function SetJSONChoices()  -- set the combobox choices
  Type.Choices = JSONChoices
  if Type.String == "" then Type.String = "Select Encode or Decode" end
end

function ProcessData()  -- process the string in the Input textbox
  if Input.String ~= "" and Type.String ~= "Select Encode or Decode" then
    if Type.String == "Encode" then 
      Output.String = rapidjson.encode(Input.String)  -- encode the string in the Input textbox 
    elseif Type.String == "Decode" then 
      local data,err = rapidjson.decode(Input.String)  -- decode the string in the Input textbox
      Output.String = data==nil and err or tostring(data)  -- prints data if valid or err if error
    end 
  end
end

function Initialization()  -- function called at the start of runtime
  ShowJSONVersion()
  SetJSONChoices()
  ProcessData()
end


-- EventHandlers
Type.EventHandler = ProcessData  -- calls process data when Type EventHandler is called
Input.EventHandler = ProcessData  -- calls process data when Input EventHandler is called


-- Start at runtime
Initialization()  -- calls Initialization at the start of runtime

Using the Example

In the Type Combo Box, select “Encode” or “Decode”. Enter the string you would like to encode or decode into the Input Text Box and the result will populate in the Output box. The Name and Version Text Boxes will populate at the start of the script.

Read/Write

Text Controller Setup

Drag in a Text Controller and name it JSON Read/Write Files. Add two Text Boxes named Input and Name, a Combo Box named Location, and a Text Indicator named Output (see screenshot).

Next, copy the Example Code to the Text Controller.

JSON Read/Write Example Code

Copy

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-- Include
rapidjson = require("rapidjson")  -- include the rapidjson library


-- Aliases
Name = Controls.Name
Location = Controls.Location
Input = Controls.Input
Output = Controls.Output


-- Constants
Locations = {"media", "design"}  -- location choices
Location.Choices = Locations  -- set location choices to the Location combobox
TestJSON = "{\"test\":test,\"Foo\":bar}"  -- test JSON string that can be used
Warning = "Cannot write JSON file in emulation mode"  -- warning used when in emulation


-- Functions
function WriteJSON(location)  -- write JSON file
  print("write json")
  local location = Location.String
  local name = Name.String
  rapidjson.dump(Input.String, location.."/"..name)  -- write JSON file to the location file path
  Timer.CallAfter(function() ReadJSON(location) end,.5)  -- call the ReadJSON function after .5 seconds and pass location
end

function ReadJSON(location)  -- read JSON file
  print("read json")
  local name = Name.String
  Output.String = tostring(rapidjson.load(location.."/"..name))  -- read JSON file and print it in the Output textbox
end

function Emulation(state)  -- function to set controls disabled and throw warnings if in emulation modee
  Input.IsDisabled = state  --  IsDisabled state driven by emulation state
  Location.IsDisabled = state  --  IsDisabled state driven by emulation state
  if state then Input.String, Location.String = Warning, Warning end  -- throw warnings if in emulation mode
end

function Initialization()  -- function called at the start of runtime
  if Location.String == "" or Location.String == Warning then Location.String = "media" end  -- set Location string if blank
  if System.IsEmulating then -- conditional that calls Emulation() passing the emulation state and calls WriteJSON if not emulating
    Emulation(true)
  else
    Emulation(false)
    WriteJSON()
  end
end


-- EventHandlers
Input.EventHandler = WriteJSON
Location.EventHandler = WriteJSON

-- Start at runtime
Initialization()  -- calls Initialization at the start of runtime

Using the Example

In the Location Combo Box, select “media” or “design”. Enter the name of the file in the Name Text Box and the file contents in the Input Text Box. The data from Input will be saved as Name in the Location folder on the Q-SYS Core processor.

Note: This file example does not work in Emulation mode.