How to read in data from a JSON file
This lesson will show you how to load a JSON file and convert the data into a LiveCode array, making it easy to use the data in your application.
JSON files are a very useful for things like storing preference settings and sharing data with other programs.
You can find out more about JSON as www.json.org.
Create a stack with a button
Ensure you have a JSON file ready to load. In this example I have is a JSON file containing the capital cities of countries. It is a simple example but your JSON file can be as complex as you need.
Open the Script Editor for the button and add this mouseUp handler.
- Ask the user to choose a file
- Load in the data from the JSON file
- Convert the JSON to a LiveCode array using the JSONToArray function.
on mouseUp pMouseButton
local tFile, tData, tArray
answer file "Choose a JSON file to load" with type "JSON|json|JSON"
if the result is not "cancel" then
put it into tFile
put url ("file:" & tFile) into tData
put JSONToArray(tData) into tArray
end if
end mouseUpPut a breakpoint on end if so we can check the array in the Variables pane of the Script Editor.
- Ensure you are in Run mode
- Click the "Load JSON" button
- Select a JSON file
- Check the Variables pane of the Script Editor to see the JSON data converted to a LiveCode array.
Converting an array to JSON
If you need to convert the contents of an array to JSON so you can save it out to file you can use the arrayToJSON function.
For example to save an array of preferences you might use
on savePreferences pPrefsArray
local tPrefsFile, tJSONData
put specialFolderPath("preferences") & "/myApp.json" into tPrefsFile
put arrayToJSON(pPrefsArray,,true) into tJSONData
put tJSONData into url ("file:" & tPrefsFile)
end savePreferencesThis will store your preferences array as JSON, ready to be read in the next time the app is started.
{
"displayMode": "Light",
"name": "Elanor",
"textSize": 14
}
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