Re: [flexcoders] Flex 2 B 2 + Cairngorm 2 - Simple Question
"user defined" and "system defined" ??? A "system defined" class was created by a user at some time in the past and then included in the class libraries... now, you write new code, extend existing classes, create entirely new classes, etc... when it's compiled it all gets glommed together. So what's the difference? The Date class is no more real or concrete than the LoginVO class. The compiler is aware of both types, where they come from, what they are derived from, what they extend, what they implement, etc. No, I agree with Tobias and fall back on the lessons I learned from Java.util.Vector... I think the reason you cast something is when its runtime type would not be known and could be anything. With a Vector you have to cast everything that you pull out because it could potentially be any type of object that was put in, and Java wants to know for sure what the type is coming out. I guess Flex is a little more forgiving and will try and default type objects in certain situations, but if you cast them then it knows for sure and would therefore be more efficient(?) Unless... the object type is not hidden, which is the case here. The compiler should know what that model is a LoginVO and it should not need to be cast. I guess in this case it's simply an efficiency thing, doesn't hurt to cast it, still works without casting it. Just confused me a little to see something cast when it didn't need it. Thanks! Darren >From: Suresh Akula <[EMAIL PROTECTED]> >Reply-To: flexcoders@yahoogroups.com >To: flexcoders@yahoogroups.com >Subject: Re: [flexcoders] Flex 2 B 2 + Cairngorm 2 - Simple Question >Date: Tue, 25 Apr 2006 14:04:35 -0700 (PDT) > >LoginVO is user defined object and where as Date is >System defined object, no need to type the these >objects. > >--Suresh > > > >--- Darren Houle <[EMAIL PROTECTED]> wrote: > > > But when? Why? In every case? If that was a > > generic, universal rule and > > you're supposed to cast everything as it's original > > object type then a > > little further in the line we should see: > > > > ' at ' + Date(model.loginDate) }" /> > > > > I'm just curious why the LoginVO is cast here. Is > > there some rule like "you > > don't have to cast an object when simply accessing > > an attribute of that > > object, but you do have to cast an object if it > > contains other objects with > > an attributes you need to access." That sounds > > kinda silly to me, that's > > why I'm asking :-) > > > > Thanks! > > Darren > > > > > > > > >From: Suresh Akula <[EMAIL PROTECTED]> > > >Reply-To: flexcoders@yahoogroups.com > > >To: flexcoders@yahoogroups.com > > >Subject: Re: [flexcoders] Flex 2 B 2 + Cairngorm 2 > > - Simple Question > > >Date: Tue, 25 Apr 2006 12:59:59 -0700 (PDT) > > > > > >Hello Darren, > > > > > > its good partice to typecast with orginal > > object > > >and invoke the object members. > > > > > >--Suresh Akula. > > > > > > > > >--- Darren Houle <[EMAIL PROTECTED]> wrote: > > > > > > > I'm fairly new to Flex and really new to > > Cairngorm > > > > and am trying to break > > > > Cg2 down and understand it (I'm not trying to > > > > understand Cg.99 and then > > > > learn Cg2, I'm just jumping into 2.) I have a > > quick > > > > question: > > > > > > > > In the Cg2 sample CairngormLogin.mxml theres a > > Label > > > > in the "loggedIn" > > > > VBox... > > > > > > > > > > > > > > > > This seems to still work fine when changed to... > > > > > > > > > > > > > > > > Is there some reason why the first form must be > > used > > > > over of the second > > > > form? If I were writing this code myself from > > > > scratch it would seem more > > > > intuitive to bind directly to the > > > > model.loginVO.username. Am I missing > > > > something? > > > > > > > > Thanks, > > > > Darren > > > > > > > > > > > > > > > > > > > > >__ > > >Do You Yahoo!? > > >Tired of spam? Yahoo! Mail has the best spam > > protection around > > >http://mail.yahoo.com > > > > &g
RE: [flexcoders] Flex 2 B 2 + Cairngorm 2 - Simple Question
IMHO, it makes no difference where the object is defined. In general, if the object returned by a function call or accessor is not the type you think it is, then you must cast it to the correct type before calling methods or accessors defined in that type. It gets a little bit complicated, but the crux of the problem is that every object has two types: its static (compile-time) and its dynamic (runtime) type. For instance I can say: var o : Object = new String( "Hello World" ); The static type of o is Object, but its actual runtime type is String. I can do this because String derives from Object. It's always possible to assign an object to an instance of a class from which that object derives. Casting tells the compiler that you want to ignore the static type of an object, and treat it as its dynamic type. For example: var myArray : Array = [ 1, 2.0, "Hello World" ]; var s : String = String( myArray[ 2 ] ); var l : int = String( myArray[ 2 ] ).length; var o : Object = myArray[ 1 ]; var n : Number = Number( o ); Arrays can hold any object. Because of this, when you get an element out of an Array, it is returned to you as an Object regardless of its actual type. Casting tells the compiler that you, the programmer, know that the returned Object is actually some other type. In the example above, I can successfully cast Objects to String and Number. The compiler will generate an error if the class of the object being cast is not a super-class of the class your casting it to. Since String and Number both derive from Object, the examples above work. But this would generate a compiler error: var b : VBox = new VBox(); var s : String = String( b ); because String does not derive from VBox. Casting can generate runtime errors as well. The compiler can only check static type information. If the actual type of the object being cast does not derive from the type it's being cast to, you will get a run-time error. For example: Var s : String = String( myArray[ 1 ] ); Because the element at position 1 in the array is a Number, and because Number does not derive from String, this command will generate a run-time error. (This might actually not generate an error -- I haven't tried it -- but only because there's some voodoo going on behind the scenes that coerces between unrelated types.) This is a very round-about way of saying that I think the Cairngorm example is wrong. There is no need to cast model.loginVO to LoginVO before accessing the username property. In the ViewLocator class, the loginVO property is typed as LoginVO, so no casting is necessary. It's runtime type matches its static type. Tobias. -Original Message- From: flexcoders@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Suresh Akula Sent: Tuesday, April 25, 2006 2:05 PM To: flexcoders@yahoogroups.com Subject: Re: [flexcoders] Flex 2 B 2 + Cairngorm 2 - Simple Question LoginVO is user defined object and where as Date is System defined object, no need to type the these objects. --Suresh --- Darren Houle <[EMAIL PROTECTED]> wrote: > But when? Why? In every case? If that was a > generic, universal rule and > you're supposed to cast everything as it's original > object type then a > little further in the line we should see: > > ' at ' + Date(model.loginDate) }" /> > > I'm just curious why the LoginVO is cast here. Is > there some rule like "you > don't have to cast an object when simply accessing > an attribute of that > object, but you do have to cast an object if it > contains other objects with > an attributes you need to access." That sounds > kinda silly to me, that's > why I'm asking :-) > > Thanks! > Darren > > > > >From: Suresh Akula <[EMAIL PROTECTED]> > >Reply-To: flexcoders@yahoogroups.com > >To: flexcoders@yahoogroups.com > >Subject: Re: [flexcoders] Flex 2 B 2 + Cairngorm 2 > - Simple Question > >Date: Tue, 25 Apr 2006 12:59:59 -0700 (PDT) > > > >Hello Darren, > > > > its good partice to typecast with orginal > object > >and invoke the object members. > > > >--Suresh Akula. > > > > > >--- Darren Houle <[EMAIL PROTECTED]> wrote: > > > > > I'm fairly new to Flex and really new to > Cairngorm > > > and am trying to break > > > Cg2 down and understand it (I'm not trying to > > > understand Cg.99 and then > > > learn Cg2, I'm just jumping into 2.) I have a > quick > > > question: > > > > > > In the Cg2 sample CairngormLogin.mxml theres a > Label > > > in the "loggedIn" > > > VBox... > > > > > > > > > > > > This seems to still work fine when c
Re: [flexcoders] Flex 2 B 2 + Cairngorm 2 - Simple Question
LoginVO is user defined object and where as Date is System defined object, no need to type the these objects. --Suresh --- Darren Houle <[EMAIL PROTECTED]> wrote: > But when? Why? In every case? If that was a > generic, universal rule and > you're supposed to cast everything as it's original > object type then a > little further in the line we should see: > > ' at ' + Date(model.loginDate) }" /> > > I'm just curious why the LoginVO is cast here. Is > there some rule like "you > don't have to cast an object when simply accessing > an attribute of that > object, but you do have to cast an object if it > contains other objects with > an attributes you need to access." That sounds > kinda silly to me, that's > why I'm asking :-) > > Thanks! > Darren > > > > >From: Suresh Akula <[EMAIL PROTECTED]> > >Reply-To: flexcoders@yahoogroups.com > >To: flexcoders@yahoogroups.com > >Subject: Re: [flexcoders] Flex 2 B 2 + Cairngorm 2 > - Simple Question > >Date: Tue, 25 Apr 2006 12:59:59 -0700 (PDT) > > > >Hello Darren, > > > > its good partice to typecast with orginal > object > >and invoke the object members. > > > >--Suresh Akula. > > > > > >--- Darren Houle <[EMAIL PROTECTED]> wrote: > > > > > I'm fairly new to Flex and really new to > Cairngorm > > > and am trying to break > > > Cg2 down and understand it (I'm not trying to > > > understand Cg.99 and then > > > learn Cg2, I'm just jumping into 2.) I have a > quick > > > question: > > > > > > In the Cg2 sample CairngormLogin.mxml theres a > Label > > > in the "loggedIn" > > > VBox... > > > > > > > > > > > > This seems to still work fine when changed to... > > > > > > > > > > > > Is there some reason why the first form must be > used > > > over of the second > > > form? If I were writing this code myself from > > > scratch it would seem more > > > intuitive to bind directly to the > > > model.loginVO.username. Am I missing > > > something? > > > > > > Thanks, > > > Darren > > > > > > > > > > > > > > >__ > >Do You Yahoo!? > >Tired of spam? Yahoo! Mail has the best spam > protection around > >http://mail.yahoo.com > > > > > >-- > >Flexcoders Mailing List > >FAQ: > http://groups.yahoo.com/group/flexcoders/files/flexcodersFAQ.txt > >Search Archives: > http://www.mail-archive.com/flexcoders%40yahoogroups.com > >Yahoo! Groups Links > > > > > > > > > > > > > > > __ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com -- Flexcoders Mailing List FAQ: http://groups.yahoo.com/group/flexcoders/files/flexcodersFAQ.txt Search Archives: http://www.mail-archive.com/flexcoders%40yahoogroups.com YAHOO! GROUPS LINKS Visit your group "flexcoders" on the web. To unsubscribe from this group, send an email to: [EMAIL PROTECTED] Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.
Re: [flexcoders] Flex 2 B 2 + Cairngorm 2 - Simple Question
But when? Why? In every case? If that was a generic, universal rule and you're supposed to cast everything as it's original object type then a little further in the line we should see: ' at ' + Date(model.loginDate) }" /> I'm just curious why the LoginVO is cast here. Is there some rule like "you don't have to cast an object when simply accessing an attribute of that object, but you do have to cast an object if it contains other objects with an attributes you need to access." That sounds kinda silly to me, that's why I'm asking :-) Thanks! Darren >From: Suresh Akula <[EMAIL PROTECTED]> >Reply-To: flexcoders@yahoogroups.com >To: flexcoders@yahoogroups.com >Subject: Re: [flexcoders] Flex 2 B 2 + Cairngorm 2 - Simple Question >Date: Tue, 25 Apr 2006 12:59:59 -0700 (PDT) > >Hello Darren, > > its good partice to typecast with orginal object >and invoke the object members. > >--Suresh Akula. > > >--- Darren Houle <[EMAIL PROTECTED]> wrote: > > > I'm fairly new to Flex and really new to Cairngorm > > and am trying to break > > Cg2 down and understand it (I'm not trying to > > understand Cg.99 and then > > learn Cg2, I'm just jumping into 2.) I have a quick > > question: > > > > In the Cg2 sample CairngormLogin.mxml theres a Label > > in the "loggedIn" > > VBox... > > > > > > > > This seems to still work fine when changed to... > > > > > > > > Is there some reason why the first form must be used > > over of the second > > form? If I were writing this code myself from > > scratch it would seem more > > intuitive to bind directly to the > > model.loginVO.username. Am I missing > > something? > > > > Thanks, > > Darren > > > > > > > > >__ >Do You Yahoo!? >Tired of spam? Yahoo! Mail has the best spam protection around >http://mail.yahoo.com > > >-- >Flexcoders Mailing List >FAQ: http://groups.yahoo.com/group/flexcoders/files/flexcodersFAQ.txt >Search Archives: http://www.mail-archive.com/flexcoders%40yahoogroups.com >Yahoo! Groups Links > > > > > > -- Flexcoders Mailing List FAQ: http://groups.yahoo.com/group/flexcoders/files/flexcodersFAQ.txt Search Archives: http://www.mail-archive.com/flexcoders%40yahoogroups.com YAHOO! GROUPS LINKS Visit your group "flexcoders" on the web. To unsubscribe from this group, send an email to: [EMAIL PROTECTED] Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.
Re: [flexcoders] Flex 2 B 2 + Cairngorm 2 - Simple Question
Hello Darren, its good partice to typecast with orginal object and invoke the object members. --Suresh Akula. --- Darren Houle <[EMAIL PROTECTED]> wrote: > I'm fairly new to Flex and really new to Cairngorm > and am trying to break > Cg2 down and understand it (I'm not trying to > understand Cg.99 and then > learn Cg2, I'm just jumping into 2.) I have a quick > question: > > In the Cg2 sample CairngormLogin.mxml theres a Label > in the "loggedIn" > VBox... > > > > This seems to still work fine when changed to... > > > > Is there some reason why the first form must be used > over of the second > form? If I were writing this code myself from > scratch it would seem more > intuitive to bind directly to the > model.loginVO.username. Am I missing > something? > > Thanks, > Darren > > > __ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com -- Flexcoders Mailing List FAQ: http://groups.yahoo.com/group/flexcoders/files/flexcodersFAQ.txt Search Archives: http://www.mail-archive.com/flexcoders%40yahoogroups.com SPONSORED LINKS Web site design development Computer software development Software design and development Macromedia flex Software development best practice YAHOO! GROUPS LINKS Visit your group "flexcoders" on the web. To unsubscribe from this group, send an email to: [EMAIL PROTECTED] Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.
[flexcoders] Flex 2 B 2 + Cairngorm 2 - Simple Question
I'm fairly new to Flex and really new to Cairngorm and am trying to break Cg2 down and understand it (I'm not trying to understand Cg.99 and then learn Cg2, I'm just jumping into 2.) I have a quick question: In the Cg2 sample CairngormLogin.mxml theres a Label in the "loggedIn" VBox... This seems to still work fine when changed to... Is there some reason why the first form must be used over of the second form? If I were writing this code myself from scratch it would seem more intuitive to bind directly to the model.loginVO.username. Am I missing something? Thanks, Darren -- Flexcoders Mailing List FAQ: http://groups.yahoo.com/group/flexcoders/files/flexcodersFAQ.txt Search Archives: http://www.mail-archive.com/flexcoders%40yahoogroups.com YAHOO! GROUPS LINKS Visit your group "flexcoders" on the web. To unsubscribe from this group, send an email to: [EMAIL PROTECTED] Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.
