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This page has not been adjusted for version 1.0 of the pico-engine |
Having a pico that maintains a collection of other picos is a pattern that is often useful.
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The complete code for this ruleset can be found at https://raw.githubusercontent.com/Picolab/pico_lessons-engine/master/collections/edu.byu.enMotion.packages/pico-engine/krl/io.picolabs.collection.krl
Creating a collection pico
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rule collection_needed {
select when grouper creation
pre {
name_prefix = event:attr("name_prefix");
group_name = name_prefix + " Rooms";
rids = "eduio.byu.enMotionpicolabs.collection;io.picolabs.subscription";
child_specs = { "name": group_name, "name_prefix": name_prefix,
"rids": rids, "color": "#002e5d" };
}
fired {
raise wrangler event "new_child_request" attributes child_specs;
}
} |
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rule collection_subscriptions {
select when wrangler child_initialized
pre {
eci = event:attr("eci");
collection_eci = get_wellKnown_eci(eci);
}
if collection_eci then noop();
fired {
raise grouper event "need_subscriptions"
attributes event:attrattrs("rs_attrs").put("collection_eci",collection_eci);
}
} |
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This KRL code will respond to the internal event, expecting the collection_eci and the child_specs given to wrangler earlier (wrangler renames it rs_attrs for some reason).
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rule collection_subscription_requests {
select when grouper need_subscriptions
foreach by_prefix(event:attr("name_prefix")) setting(room_name,tag_id)
pre {
eci = building:eci(tag_id);
wellKnown_Tx = get_wellKnown_eci(eci).klog("wellKnown_Tx");
}
if wellKnown_Tx then every {
event:send({"eci":eci,"domain":"wrangler","type":"subscription",
"attrs": { "wellKnown_Tx": event:attr("collection_eci"),
"Rx_role": "member", "Tx_role": "collection",
"name": tag_id, "channel_type": "subscription" }
})
}
} |
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meta {
use module eduio.byupicolabs.enMotion.collection alias collection
shares some_function
}
global {
some_function = function() {
collection:members()// some further processing
}
}
rule some_rule {
select when something required
foreach collection:members() setting(subs)
// some action/postludes for each subs
} |
and specify additional processing in some_function (defined in lines 6-8) that it shares (in line 3) to endpoints, and/or specify rules like some_rule (defined in lines 10-14) that take action on the collection's members when certain events occur.
When a member is added
Since members of the collection are determined by subscriptions, your ruleset can listen for wrangler:subscription_added events to do something when a new member joins your collection. Since your pico might participate in other subscriptions, only those in which the roles are "collection" and "member" would be applicable.
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rule new_member {
select when wrangler subscription_added
pre {
pertinent = event:attr("Rx_role")=="collection"
&& event:attr("Tx_role")=="member";
}
if pertinent then noop();
fired {
raise collection event "new_member" attributes event:attrs
}
} |
The event attributes available are those surrounding a subscription in general. Some of these might be useful when a new member arrives into your collection
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When a member is removed
Your ruleset might wish to listen to the event wrangler:subscription_removed which will be raised when a subscription is removed from your pico. Such events which are applicable to membership in your collection could then be handled appropriately.
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rule new_member {
select when wrangler subscription_removed
pre {
pertinent = event:attr("Rx_role")=="collection"
&& event:attr("Tx_role")=="member";
}
if pertinent then noop();
fired {
raise collection event "member_removed" attributes event:attrs
}
} |