从我的应用程序访问Facebook画布URL参数

Question

I'm making a facebook canvas app (a game) and I want my players to use links with url parameters that link to different areas in the game, ie

https://apps.facebook.com/mgatlandtestapp?level=emeraldhillzone

How do I access the level=emeraldhillzone information in my app (either client-side with javascript in an iFrame, or server-side as a node.js application)

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Things I've tried so far:

1. This 4-year-old answer says it's possible to in the client-side code but doesn't say how (sorry if I'm missing something obvious! window.location gives the location of my heroku server, not the facebook url.)

2. Some of the facebook documentation made me think this would work:

Use a url in the form https://apps.facebook.com/mgatlandtestapp?app_data=yourDataHere then on the server side get the signed request sent to the server and it will contain an app_data field.

However when I did this, the signed request did not contain an app_data field.

After reading more, I think the app_data thing only works if the app is being loaded within a facebook Page Tab, not a facebook Canvas Page.

Answer 1

Facebook sends an initial POST to your app, which includes the url parameters. You can access the url parameters from in that POST request.

I used this url to load the page:

https://apps.facebook.com/mgatlandtest/?level=emeraldhillzone

I used this code in my node.js server app to serve the request

app.post('/*', function(request, response) {
  console.log('url parameters:');
  console.log(request.query);
  response.redirect('/');
});

The output in the node console was:

url parameters:
{ level: 'emeraldhillzone' }

You could then use the parameters to redirect to a different page.

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This was actually really simple, once I got past all the distracting misinformation. The key was searching for 'deep linking' (instead of 'url parameters'), which brought up this answer