On March 2, 2004 08:20 pm, Shawn wrote: > "type" is used in Javascript, so consider it a reserved word. I know you > can override some reserved words, but that's asking for trouble.
I knew someone was gonna notice that :) > > Also, you're treeinfo function is slightly wrong. It is a member function > of a tree, but makes reference to an object it doesn't know about > (my_forest). > Replace "my_forest" inside the treeinfo function with "this". But even > then this will have problems. The Tree class doesn't define a "type" > property. Yeah, which I know how to fix now thanks to you. Im still boggled as to why it could see my_forest was an object but couldn't see its member vars. Oh well, its trivial, but interesting. > > I would rework your classes a little to put the TreeInfo function as a > member function on the Forest class, and pass in the Tree instance you want > the information from. Of course, there are other ways to do this, and I > realize this is only sample code - your real code may not be doing this.... Applying the same concept should work in my actual code. Guess I was thinking so hard my brain quit. > > As for your questions, yes the this.trees[i] in your MakeTrees function > does point to your forest object. This is because the MakeTrees function > is a member function (or method) of the Forest class. If you call > MakeTrees directly (i.e. x = MakeTrees(), not x=my_forest.MakeTrees() ), > then "this" refers to the function itself (if I remember right), and you'll > have problems. makes sense. > > So, your forest class can have tree objects in it. The tree class and it's > methods can also make reference to "this", but at that point, "this" is > refering to the tree object. > > Oh, one last thing. In your Forest function, the line "trees = new > Array();" should read "this.trees = new Array();". If you don't make this > change, the trees variable will loose scope when the function is done. a minor oversight in my 'type this example as fast as I can' mindset. > > Not really a well laid out response, but I hope it points you in the right > direction. I'm "very" familiar with JS classes, so feel free to email me > off list if you need any other tips/help. Thanks a lot Shawn, this should be sufficient to get me going again. Hopefully I won't need to contact you off-list, but thanks for the offer. > > Shawn > > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] > Behalf Of Nick W > Sent: Tuesday, March 02, 2004 4:14 PM > To: CLUG General > Subject: [clug-talk] OT - Javascript frustration > > > Sorry for the OT post but this makes no sense and every source I read tells > me > this should work. > > I have a stupid problem with a script Im writing. I have an object which > contains an array of objects, which contain image objects. I set the > onmouseover property of the images to run a function which needs data from > one of the outermost object's properties. The said function can see the > object, but not its properties. OK thats clear as mud, let me try a > simplified example... > > <begin lame example> > > function Forest() > { > this.type = 'rainforest'; > trees = new Array(); > > this.MakeTrees = MakeTrees; > } > > function MakeTrees() > { > for(i = 0; i < 1000; i++)//make 1000 trees > { > this.trees[i] = new Tree(); > } > } > > function Tree() > { > this.img = new Image(); > //pretend I set the this.img properties here... > this.img.onmouseover = TreeInfo; > } > > function TreeInfo() > { > alert(typeof(my_forest)); > alert('This tree is in a ' + my_forest.type); > } > > my_forest = new Forest(); > my_forest.MakeTrees(); > <end lame example> > > When you mouseover a tree, the first alert in TreeInfo() will tell you > my_forest is an object, but the 2nd one will spit out "This tree is in a > undefined". Why?? > > Note, the above code was written very quickly and is probably unuseable, > but it serves its purpose as a lame example. > > Its obviously some sort of scope issue with Java I dont get. AFAIK, > my_forest > should be global in this case. My other question is in MakeTrees() does the > 'this' in 'this.trees[i]' point to my_forest? Of course the whole thing > could > be FUBAR.... > > tks. > -- > Nick W (nickw77 at shaw.ca) > Registered Linux User #324288 (http://counter.li.org) > MSN Messenger: [EMAIL PROTECTED] > Yahoo: foolish_gambit > ICQ: 303276221 > It's not our fault, we're outnumbered by stupid people ten to one. > > _______________________________________________ > clug-talk mailing list > [EMAIL PROTECTED] > http://clug.ca/mailman/listinfo/clug-talk_clug.ca > > > _______________________________________________ > clug-talk mailing list > [EMAIL PROTECTED] > http://clug.ca/mailman/listinfo/clug-talk_clug.ca -- Nick W (nickw77 at shaw.ca) Registered Linux User #324288 (http://counter.li.org) MSN Messenger: [EMAIL PROTECTED] Yahoo: foolish_gambit ICQ: 303276221 It's not our fault, we're outnumbered by stupid people ten to one. _______________________________________________ clug-talk mailing list [EMAIL PROTECTED] http://clug.ca/mailman/listinfo/clug-talk_clug.ca
