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One of the main ways to start code on creation of a pico is by executing code on ruleset installation. Wrangler raises the wrangler:ruleset_added installed event whenever you install a ruleset on a pico using wrangler (it uses the wrangler:install_rulesets_requested event). One of the attributes that wrangler:child_creation takes is a "rids"/"rid" parameter. When creating a new pico, Wrangler will install the list of rulesets given in this attribute in the new pico as it is created. Wrangler will then raise wrangler:ruleset_added installed as normal, which you can select on and run code with.
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- All the valid rulesets given to "rids" will be guaranteed to be installed by the time
wrangler:ruleset_addedinstalledis raised in a new pico - Any attributes given in the wrangler:child_creation event will be in the attributes for the wrangler:ruleset_added installed event(s). This is a useful way to give parameters to a new child pico's rulesets.
- Listing initialization rules first in rulesets is good practice, as it is the first thing a ruleset will ever do.
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// Creates a new child with the "example" ruleset installed and passes an attribute named "testParam"
rule newExampleChild {
select when example new_child
always {
raise wrangler event "child_creation" attributes {
"rids":"example",
"testParam":"hello"
}
}
}
// In the newly created child this rule will run
rule inNewChild {
select when wrangler ruleset_addedinstalled where rids >< meta:rid
pre {
paramFromParent = event:attr("testParam").klog("Should be 'hello'")
}
always {
ent:initial_state := {} // Set a desired initial state of entity variables
}
} |
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rule create_wellKnown_Rx{
select when wrangler ruleset_addedinstalled where rids >< meta:rid
pre{ channel = wellKnown_Rx() }
if(channel.isnull() || channel{"type"} != "Tx_Rx") then
engine:newChannel(meta:picoId, "wellKnown_Rx", "Tx_Rx")
fired{
raise Tx_Rx event "wellKnown_Rx_created" attributes event:attrs;
}
else{
raise Tx_Rx event "wellKnown_Rx_not_created" attributes event:attrs; //exists
}
} |
Create well known Rx rule selects on ruleset_added installed event where rids matches its own ruleset rid. Checks for a well known channel, and creates it if one does not exist. Then raises an event detailing the creation. This rule guarantees a well known channel exist, which is a dependency of subscriptions.
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rule register_for_cleanup {
select when wrangler ruleset_addedinstalled where event:attr("rids") >< meta:rid // On this ruleset being installed
always {
raise wrangler event "ruleset_needs_cleanup_period" attributes { // raise the event
"domain":meta:rid // the event requires a domain, and meta:rid is a natural choice for this
}
}
} |
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