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[REBOL] Object lesson, please?

From: SunandaDH::aol::com at: 23-Oct-2003 11:19

I need a function that expands an object to add extra fields. So I've written one. See below. From an engineering perspective, it works fine. From a REBOL elegance viewpoint that "return do mold obj" goes clunk in my brain. Is there a better way? A bit of background....I got a system that holds persistent data as molded objects in files. I need to add fields that weren't dreamt of in the initial release. But I don't need to worry about circular references or the object being referenced elsewhere. The simplest solution is to apply a template of all possible fields to an object each time we read it. The function below is intended to do that. The "return do mold obj" seems necessary to stop inner objects that aren't in the original being the 'same? as the template object. How can I do this more elegantly, please? ;;========== the function ========== Rebol [] update-object: func [obj [object!] template [object!] /local ] [ foreach field next first template [ if error? try [obj/:field] [ obj: construct/with reduce [to-set-word field template/:field] obj ] if object? template/:field [ obj: construct/with reduce [to-set-word field update-object obj/:field template/:field] obj ] ] ;; for return do mold obj ;; added objects are independent beings. ;;;;return obj ;; added objects are the 'same? as template ] ;; func ;; ========== Some test data data ========== test-template: make object! [ a1: "initial data value" a2: "not in test object" a3: make object! [ a3-1: 1-oct-2003 a3-2: make object! [a3-2-1: "sss" a3-2-2: "also not in test object" ] a3-3: "rebol [halt]" ;; dangerous value if loaded a3-4: reduce [now/precise] ] a4: make object! [] ;; empty object -- not in test a5: make object! [a5-1: a5-2: a5-3: true] a6: a7: a8: none a9: make object! [a9-1: a9-2: a9-3: false] ] test-object: make object! [ a1: "got a value" a3: make object! [a3-1: false a3-2: make object! [a3-2-1: "also got a value" ] ] ] loop 10 [print ""] res1: update-object test-object test-template wait 0.1 ;; see if nows cause a problem -- they shouldn't in this case res2: update-object res1 test-template print "test failure messages follow...." if strict-not-equal? mold res1 mold res2 [Print "Something didn't work"] if same? res1/a4 test-template/a4 [print "we've got cloning!"] if same? res1/a9 test-template/a9 [print "we've got cloning!"] ==================== Thanks! Sunanda