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Since most of the heavy lifting is done by the Subscriptions ruleset, it is easy to initiate, approve, and use subscriptions inside of your own rulesets.
Prepare for this section by manually creating three child picos of your owner pico. Install this ruleset into your owner pico: https://raw.githubusercontent.com/b1conrad/krl-sample/master/krl/mischief/mischief.krl and install this ruleset into your Mischief pico: https://raw.githubusercontent.com/b1conrad/krl-sample/master/krl/mischief/mischief.owner.krl and finally, install this ruleset into each of your thing picos: https://raw.githubusercontent.com/b1conrad/krl-sample/master/krl/mischief/mischief.thing.krl
Initiating subscriptions by introduction
It is possible to initiate a subscription with a rule running in a pico which already has in its possession the ECI's of the two picos which need to be related by the subscription. For example, once we Once you have set up the three child picos, Mischief, Thing1, and Thing2, we can install a ruleset into each of them and the owner pico. Simple examples are available in this repository, and installed their respective rulesets, study the code and prepare for the introductions.
The owner pico already has all three of the other ECI's in its array of children (maintained by the io.picolabs.pico aka Wrangler ruleset), but it doesn't know which is which. So we added this rule to allow it to distinguish between the Mischief pico (which identifies itself by ECI) and the Thing1 and Thing2 picos.
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The ruleset for the Mischief pico sets up a button "mischief/identity" in that pico's Testing tab which will send this event to the owner picothat pico's Testing tab which will send this event to the owner pico. Navigate to the Testing tab of the Mischief pico and click the button. Doing so will send the event mischief:who to the owner pico, and that event will trigger the rule shown above. You can check the result of this calculation by looking at the entity variables held by the mischief.owner ruleset in the Rulesets tab of the Owner Pico.
Once the owner pico has all of the ECI's, the code to introduce the Mischief pico to each of the thing picos is straight-forward.
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The ruleset also sets up a button in the owner pico's Testing tab, "mischief/subscriptions" to send the event that causes this rule to evaluate. Navigate to the Testing tab for the Owner Pico to click on this button.
The final step is that a rule selecting on wrangler/inbound_pending_subscription_added in is in each of the thing picos (the ruleset mischief.thing), and this will complete the subscription process. You can see the results by refreshing the UI and navigating to the Subscriptions tab for any of the picos involved in one of the two subscriptions.
Initiating subscriptions by direct request
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As in the case of introductions, the target pico must have a rule selecting on wrangler/inbound_pending_subscription_added which will complete the subscription process by raising the wrangler/pending_subscription_approval event.
Writing rules that use subscriptions
Suppose that we wanted the Mischief pico to respond to a mischief/hat_lifted event and send the same event to all of the thing picos that it controls. Assuming that you have arranged to use Subscriptions as a module in the meta block, as in
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