View source for Scripting: Consumer Functions

In Waltz, some functions may require you to provide a [[Type: Consumer|Consumer]] object to process data. This pattern is generally used when the function you are using may not immediately have a response available to be processed. This can occur when a function needs to perform a task on the network, but the entire show should not wait for the response, only the bit of code that needs to handle the response.

Consumers in Waltz are just [https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Functions JavaScript functions], taking some number of arguments. No return value is expected of a consumer function.

==Defining a Consumer Function==
For this example, we will work with a [[Node: Watchout Media Server|Watchout Media Server]] node, which defines a function <code>getCurrentCue(…)</code> that requires a consumer. The Consumer for that function returns a single [[Type: WoControlCue|WoControlCue]], off of which we want to print the <code>name</code> parameter. This can be achieved with the following snippet of code.
 $.watchout.getCurrentCue(function(cue) {
     print(cue.name);
 });
Notice that we defined a function that takes a single argument, and named that argument <code>cue</code>. The name of the argument is not important and could easily be any other valid name, but the number of arguments is important.

==Using a Script Function as a Consumer==
Because any function can be a consumer, we can use a [[Node: Script Function|Script Function]] node as our consumer, using its <code>consumer</code> property. In this example, we have a Script Function node that defines a single argument <code>name</code>, and a body of <code>print(cue.name);</code>. We can then produce an identical result to our previous example with the following line of script.
 $.watchout.getCurrentCue($.scriptFunction.consumer);
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