Standards as Constraints

In other databases or languages, you are able to join properties or perform aggregations. We can do this in Standard by creating a constraint of type standard.

    
    truck: TRCK: @VHL {
        protected owner standard @PER OWNR *
        protected max_weight double MXWGHT
    }
    

Now when accessing the owner constraint, you can access it like @USR or OWNR. When this record is saved, the constraint value is the record id of the parent Standard record.

    
    #Get Trucks where vehicle model is 'Tesla', limit 1
    foundTruck [TRCK] <VHL.MK "Tesla" LIMIT 1>

    #Prints truck owner's first name
    print foundTruck.OWNR.FNAME

    #Also prints truck owner's first name
    print foundTruck.owner.firstname

    #again
    print foundTruck.USR.firstname
    

If your Standard references the same Standard in more than one constraint, Standard will select the first constraint that uses that Standard if accessed that way.

    
    truck: TRCK: @VHL {
        protected owner standard @PER OWNR *
        protected driver standard @PER DRVR *
    }

    #Ini empty object
    truck @TRCK

    print truck PER firstname #Will only ever print the owner's firstname
    print truck driver firstname #Now we print driver's firstname