By using Snap Kit within your app, you can create Dynamic Lenses which allows your Lens to receive information from outside the Lens itself. For example, you can pass in information like the current score of a sports game to change the effects of your Lens, or modify the look of a hat that the Snapchatter is wearing.

Note: In order to pass information into the Lens, you must launch the Lens via a Creative Kit integration. To learn more about Creative Kit, check out the following iOS and Android guide 

How it Works

When you launch your Lens with Creative Kit, you’re able to pass in information and read it in when the Lens is opened. 

For example, if you add the following information on the Creative Kit side SnapLensLaunchData:

• game_score: [23,10]
• team_names: [“Red Team”, “Pink Team”]

You’d be able to read this content in the Lens by creating a script:

var store = global.launchParams;
var teams = store.getStringArray(“team_names”);
print( teams[0] + “ v.s. “ + teams[1] );
var myFloatArray = launchParams.getFloatArray(“game_score”);
print("Score: " + myFloatArray[0] + " to " + myFloatArray[1]);

And use it to feed logic in the same way you’d use any script. 

Tip: The launch parameters uses a similar API to the GeneralDataStore

You can pass parameters of type:

• Strings
• Arrays of Strings
• Numbers
• Arrays of Numbers

Note: Launch parameters are not available in Lens Studio or when pushed to the device. 

Dynamic Lens Template 

To help with development, you can download this template.

This template provides you with a framework to set up fallback data, and see how a passed in parameter would affect your Lens. 

Using the Wrapper

Instead of accessing the launchParams directly you can use this wrapper:

var launchParams = global.getLaunchParams(); 

This will automatically provide you with either the real launch parameters, or the fallback data depending on what is available. 

Choosing Fallback Data

If your Lens is launched without the expected launchParams (e.g. launched outside of your app), it will use a predefined fallback data. The Lens will check whether real data are available based on a Key to Check. 

To set this, click the Launch Params Wrapper object in the Objects panel, and fill in the field next to Key To Check. 

If this key is not available, the Lens will use the data set chosen in Fallback Data. Choose this by changing the dropdown next to Fallback Data on the same script component. 

Testing Launch Parameters 

Since launchParams are not available in Lens Studio, choosing different fallback data is a quick way to test out your different parameters. Click on the dropdown next to Fallback Data to try different data sets. 

Adding Data 

You can set up your data sets by modifying the FallbackDataSource script found in the Resources panel. Double click on the script to open it in the Script Editor. 

Then, modify the dataSet function to add in your data. These dataSet functions correspond to the drop down found in the LaunchParamsWrapper script on the LaunchParamsWrapper object.

That is, this function: 

function dataSet1() {
   launchParams.putFloatArray ("game_score", [23 , 10]);
   launchParams.putFloatArray ("winning_team_color", [1, 0, 0]);
   launchParams.putStringArray ("team_names", ["Red Team", "Pink Team"]);
}

Will be selected when Data Set 1 is selected in the Inspector panel. 

To add your data set, you can simply put your data as you would in general data store.

       launchParams.putString("testString", "Test string 1");
       launchParams.putStringArray("testStringArray", ['One', 'Two', 'Tree']);
       launchParams.putFloat("testNumber", 1256.0);
       launchParams.putFloatArray("testNumberArray", [1, 2.5465, 3.14]);

Tip: By default, there are 6 data set slots. However, you can add more as you wish. To do this, add a new function for the data set, and append it to the script.api.data array. Then, modify the fallbackData dropdown found in the LaunchParamsWrapper script found in the Scripts folder. Take a look at the Custom Script UI input to learn more. 

Reading Data

You can read the params as you would with the General Data Store.  For example, to access a string:

var stringParamName = "testString";
if (launchParams && launchParams.has(stringParamName)) {
   var myString = launchParams.getString(stringParamName);
   // use one of scenarios depending of the value of this variable
   } else {
  //use some fallback scenario here in case if launch parameters were not set or there is no value with this name
}

Tip: Take a look at the GameScoreController script to see an example of how you can use launchParams to modify your Lens!

Publishing your Dynamic Lens

The process of publishing your Dynamic Lens is the same as any other Lens. Take a look at the Submitting guide for more information. 

Optionally, you may want to make the Lens not discoverable outside of your app. To do this, click on the three dots next to the Share button in your My Lenses, and enable Do Not Promote. 

Warning: This step is especially important if you’ve not designed your Lens with fallback content.

Getting your SnapLensContent ID

To get the ID number used to connect your app to the Snapchat Lens, contact your Snap liaison and share with them your Lens ID which is found underneath your Snapcode. Click on it to copy it to your clipboard.