AS convention: Public member variables?! What of encapsulation?

[WillyRay]

Ok... I'm not asking "can I use getters and setters to properly encapsulate my AS classes?".  I'm asking why does the accepted ActionScript convention seem to be public member variables?  Every example I see, every book I buy... public properties all the time.  

Aren't we Flex developers just as worried about uncontrolled access to these members as, say, Java developers?  Is there some feature of the language that I'm missing that protects against bad data being set into public properties?

/Willy  

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[Barney Boisvert]

ActionScript, unlike Java, lets you transparently override public
properties with implicit getters and setters.  So you can start with a
public property, and then later decide to use a getter/setter pair
without changing the API of your class.  With Java, you can't do that,
so you HAVE to declare the getter/setter pair up front.

As a concrete example:

public class Person {
  public var name:String;
}

can be used like this:

p = new Person();
p.name = "fred";
trace(p.name);

Later, you can change the class to this:

public class Person {
  private var _name:String;
  public function get name():String {
    return _name;
  }
  public function set name(name:String):String {
    _name = name;
  }
}

After doing that, you can still reference the class in exactly the
same way as before; ActionScript takes care of the implicit
getter/setter magic internally, so you don't have to worry.  The net
is that you're not sacrificing encapsulation, you're just not having
to write a bunch of boilerplate code until you actually need to.

cheers,
barneyb

On Tue, Nov 10, 2009 at 12:18 PM, Willy Ray <willyray@...> wrote:
>
> Ok... I'm not asking "can I use getters and setters to properly encapsulate my AS classes?".  I'm asking why does the accepted ActionScript convention seem to be public member variables?  Every example I see, every book I buy... public properties all the time.
>
> Aren't we Flex developers just as worried about uncontrolled access to these members as, say, Java developers?  Is there some feature of the language that I'm missing that protects against bad data being set into public properties?
>
> /Willy
>
>

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[Paul Kukiel-2]

As well as for VO's back to ColdFusion they need to be public.

Paul.

-----Original Message-----
From: Barney Boisvert [mailto:bboisvert@...]
Sent: Tuesday, November 10, 2009 3:32 PM
To: flex
Subject: Re: AS convention: Public member variables?! What of encapsulation?


ActionScript, unlike Java, lets you transparently override public
properties with implicit getters and setters.  So you can start with a
public property, and then later decide to use a getter/setter pair
without changing the API of your class.  With Java, you can't do that,
so you HAVE to declare the getter/setter pair up front.

As a concrete example:

public class Person {
  public var name:String;
}

can be used like this:

p = new Person();
p.name = "fred";
trace(p.name);

Later, you can change the class to this:

public class Person {
  private var _name:String;
  public function get name():String {
    return _name;
  }
  public function set name(name:String):String {
    _name = name;
  }
}

After doing that, you can still reference the class in exactly the
same way as before; ActionScript takes care of the implicit
getter/setter magic internally, so you don't have to worry.  The net
is that you're not sacrificing encapsulation, you're just not having
to write a bunch of boilerplate code until you actually need to.

cheers,
barneyb

On Tue, Nov 10, 2009 at 12:18 PM, Willy Ray <willyray@...> wrote:
>
> Ok... I'm not asking "can I use getters and setters to properly
encapsulate my AS classes?".  I'm asking why does the accepted ActionScript
convention seem to be public member variables?  Every example I see, every
book I buy... public properties all the time.
>
> Aren't we Flex developers just as worried about uncontrolled access to
these members as, say, Java developers?  Is there some feature of the
language that I'm missing that protects against bad data being set into
public properties?
>
> /Willy
>
>



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[WillyRay]

@barneyb, maybe I'm just being a curmudgeonly Java engineer, but it
still gives me the creeps to see all those public members.  I see your
point, though.  By using the implicit getters and setters only as
needed I can change the functionality without changing the "signature"
of the class.   This seems to assume, however that most setters are
simply {this.myVar = myVar;}, and are actually a waste of time.  I'll
concede that many of them may be, but they're generated, and I don't
actually have to write them.  I see the value, in a shared-code
environment of being able to add the setter without having to update
calling code.

@Paul, We're using BlazeDS with Tomcat, and it's the same way... It
expects the AS class to have the public properties.  But that seems to
me to be more of a response to the established convention rather than
something that's inherent to the AMF communications.    They could
just as easily used a Beans kind of approach and retrospected the
class for set*() and get*().  Doesn't Mach-ii do that on its beans?

Anyway, thanks guys,  nice to at least hear a well-reasoned response
to the question I actually asked.  Usually when I bring this up the
answer I get is, "You want setters?  Just write 'em, and leave me
alone!"

/w

On Tue, Nov 10, 2009 at 1:33 PM, Paul Kukiel <kukielp@...> wrote:

>
> As well as for VO's back to ColdFusion they need to be public.
>
> Paul.
>
> -----Original Message-----
> From: Barney Boisvert [mailto:bboisvert@...]
> Sent: Tuesday, November 10, 2009 3:32 PM
> To: flex
> Subject: Re: AS convention: Public member variables?! What of encapsulation?
>
>
> ActionScript, unlike Java, lets you transparently override public
> properties with implicit getters and setters.  So you can start with a
> public property, and then later decide to use a getter/setter pair
> without changing the API of your class.  With Java, you can't do that,
> so you HAVE to declare the getter/setter pair up front.
>
> As a concrete example:
>
> public class Person {
>  public var name:String;
> }
>
> can be used like this:
>
> p = new Person();
> p.name = "fred";
> trace(p.name);
>
> Later, you can change the class to this:
>
> public class Person {
>  private var _name:String;
>  public function get name():String {
>    return _name;
>  }
>  public function set name(name:String):String {
>    _name = name;
>  }
> }
>
> After doing that, you can still reference the class in exactly the
> same way as before; ActionScript takes care of the implicit
> getter/setter magic internally, so you don't have to worry.  The net
> is that you're not sacrificing encapsulation, you're just not having
> to write a bunch of boilerplate code until you actually need to.
>
> cheers,
> barneyb
>
> On Tue, Nov 10, 2009 at 12:18 PM, Willy Ray <willyray@...> wrote:
>>
>> Ok... I'm not asking "can I use getters and setters to properly
> encapsulate my AS classes?".  I'm asking why does the accepted ActionScript
> convention seem to be public member variables?  Every example I see, every
> book I buy... public properties all the time.
>>
>> Aren't we Flex developers just as worried about uncontrolled access to
> these members as, say, Java developers?  Is there some feature of the
> language that I'm missing that protects against bad data being set into
> public properties?
>>
>> /Willy
>>
>>
>
>
>
>

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