Happy New Year Scalars!

Consider the following trait:

 trait Property[T] {
   protected var _value : T = _

   implicit def value : T = _value

   implicit def value_=(newValue : T) {
     _value = newValue
   }
 }

If a definition like this:

 class Foo {
   object Bar extends Property[String]
 }

could be expanded by automatically adding methods that corresponded to
the object name like this:

 class Foo {
   object Bar extends Property[String]
   def bar : String = Bar.value
   def bar_=(newValue : String) = Bar.value_=(newValue)
 }

then we might have a workable syntax for properties and maybe other
things too.  Here's the same example with a default value and an
overridden setter:

 class Foo {
   object Bar extends Property[String] {
     value = "Hello World!"

     override def value_=(newValue : String) {
        super.value = newValue
        println("Value changed to " + newValue)
     }
   }
 }


Fatally flawed or worth further consideration?

Regards,

Andrew Foggin

Hey Andrew,

checked it out a bit and I have some questions.

1) How does one iterate over all properties contained withing type X?
2) How does one set the value of Property Y when passed a reference to property Y and a reference to type X (which is the enclosing type of Y)?
3) What is the actual type of a property? I.e. considering:

class Foo
{
    object Bar extends Property[String]
}

Is Bar a Property[Foo,String]?
Or a FooProperty[String]?

(This question arises if someone wants to create a method/function that only accepts Properties on Foos)

And I think we'd need syntactic sugar for this.
It's _not_ Beginner friendly to define a property as an object.
A property is a property and should be declared as one.

class Foo
{
   property Name : String // == object Name extends Property[Foo,String] + the probably needed getter/setter methods
}

Feedback?

Cheers,
Viktor

On Jan 1, 2008 4:56 PM, Andrew Foggin <andy <at> foggin.net > wrote:

Happy New Year Scalars!

Consider the following trait:

 trait Property[T] {
   protected var _value : T = _

   implicit def value : T = _value

   implicit def value_=(newValue : T) {
     _value = newValue
   }
 }

If a definition like this:

 class Foo {
   object Bar extends Property[String]
 }

could be expanded by automatically adding methods that corresponded to
the object name like this:

 class Foo {
   object Bar extends Property[String]
   def bar : String = Bar.value
   def bar_=(newValue : String) = Bar.value_=(newValue)
 }

then we might have a workable syntax for properties and maybe other
things too.  Here's the same example with a default value and an
overridden setter:

 class Foo {
   object Bar extends Property[String] {
     value = "Hello World!"

     override def value_=(newValue : String) {
        super.value = newValue
        println("Value changed to " + newValue)
     }
   }
 }


Fatally flawed or worth further consideration?

Regards,

Andrew Foggin

--
_____________________________________
/                                                                 \
       /lift/ committer ( www.liftweb.net)
     SGS member (Scala Group Sweden)
 SEJUG member (Swedish Java User Group)
\_____________________________________/

Addendum:

3) And how do they interact with constructors?

i:e

class Foo
{
    property Bar : String
    property Baz : Int
}

val f : Foo = new Foo(Bar = "wawawowa", Baz = "Yeehaw") ?

Cheers,
-Viktor

On Jan 1, 2008 7:57 PM, Viktor Klang < viktor.klang <at> gmail.com> wrote:

Hey Andrew,

checked it out a bit and I have some questions.

1) How does one iterate over all properties contained withing type X?
2) How does one set the value of Property Y when passed a reference to property Y and a reference to type X (which is the enclosing type of Y)?
3) What is the actual type of a property? I.e. considering:

class Foo
{
    object Bar extends Property[String]
}

Is Bar a Property[Foo,String]?
Or a FooProperty[String]?

(This question arises if someone wants to create a method/function that only accepts Properties on Foos)

And I think we'd need syntactic sugar for this.
It's _not_ Beginner friendly to define a property as an object.
A property is a property and should be declared as one.

class Foo
{
   property Name : String // == object Name extends Property[Foo,String] + the probably needed getter/setter methods
}

Feedback?

Cheers,
Viktor

On Jan 1, 2008 4:56 PM, Andrew Foggin <andy <at> foggin.net > wrote:

Happy New Year Scalars!

Consider the following trait:

 trait Property[T] {
   protected var _value : T = _

   implicit def value : T = _value

   implicit def value_=(newValue : T) {
     _value = newValue
   }
 }

If a definition like this:

 class Foo {
   object Bar extends Property[String]
 }

could be expanded by automatically adding methods that corresponded to
the object name like this:

 class Foo {
   object Bar extends Property[String]
   def bar : String = Bar.value
   def bar_=(newValue : String) = Bar.value_=(newValue)
 }

then we might have a workable syntax for properties and maybe other
things too.  Here's the same example with a default value and an
overridden setter:

 class Foo {
   object Bar extends Property[String] {
     value = "Hello World!"

     override def value_=(newValue : String) {
        super.value = newValue
        println("Value changed to " + newValue)
     }
   }
 }


Fatally flawed or worth further consideration?

Regards,

Andrew Foggin

--
_____________________________________
/                                                                 \
       /lift/ committer ( www.liftweb.net)
     SGS member (Scala Group Sweden)
 SEJUG member (Swedish Java User Group)
\_____________________________________/

--
_____________________________________
/                                                                 \
       /lift/ committer ( www.liftweb.net)
     SGS member (Scala Group Sweden)
 SEJUG member (Swedish Java User Group)
\_____________________________________/

Addendum 2:

So I guess this boils it down to my feature list for properties:

1) Intuitive syntax: i.e "property X of type Y"
2) instance-access: i.e. (new Foo).name
3) static-access: i.e. Foo.Name or Foo.name
4) instance-read: i.e. val s = (new Foo).name
5) static-read: i.e. Foo.Name or Foo.name.get(new Foo)
6) instance-write: i.e. (new Foo).name = "wawawowa"
7) static-write: i.e. Foo.Name.set(new Foo, "wawawowa")
8) instance-enumeration: (new Foo).properties
9) static-enumeration: Foo.properties
10) seamless integration with constructors: i.e. new Foo(Name = "wawawowa", Bar = "Yeehaw")
11) ability to extrapolate information from properties like the type of the value that it holds, it's name, it's validator etc
12) ability to tie metadata to properties, iether though annotations or other means (mixins etc)

I've probably forgot something here so I'll reserve the rights to go back and add stuff here. :)

Discuss!

Cheers,
Viktor

On Jan 1, 2008 9:40 PM, Viktor Klang < viktor.klang <at> gmail.com> wrote:

Addendum:

3) And how do they interact with constructors?

i:e

class Foo
{
    property Bar : String
    property Baz : Int
}

val f : Foo = new Foo(Bar = "wawawowa", Baz = "Yeehaw") ?

Cheers,
-Viktor

On Jan 1, 2008 7:57 PM, Viktor Klang < viktor.klang <at> gmail.com> wrote:

Hey Andrew,

checked it out a bit and I have some questions.

1) How does one iterate over all properties contained withing type X?
2) How does one set the value of Property Y when passed a reference to property Y and a reference to type X (which is the enclosing type of Y)?
3) What is the actual type of a property? I.e. considering:

class Foo
{
    object Bar extends Property[String]
}

Is Bar a Property[Foo,String]?
Or a FooProperty[String]?

(This question arises if someone wants to create a method/function that only accepts Properties on Foos)

And I think we'd need syntactic sugar for this.
It's _not_ Beginner friendly to define a property as an object.
A property is a property and should be declared as one.

class Foo
{
   property Name : String // == object Name extends Property[Foo,String] + the probably needed getter/setter methods
}

Feedback?

Cheers,
Viktor

On Jan 1, 2008 4:56 PM, Andrew Foggin <andy <at> foggin.net > wrote:

Happy New Year Scalars!

Consider the following trait:

 trait Property[T] {
   protected var _value : T = _

   implicit def value : T = _value

   implicit def value_=(newValue : T) {
     _value = newValue
   }
 }

If a definition like this:

 class Foo {
   object Bar extends Property[String]
 }

could be expanded by automatically adding methods that corresponded to
the object name like this:

 class Foo {
   object Bar extends Property[String]
   def bar : String = Bar.value
   def bar_=(newValue : String) = Bar.value_=(newValue)
 }

then we might have a workable syntax for properties and maybe other
things too.  Here's the same example with a default value and an
overridden setter:

 class Foo {
   object Bar extends Property[String] {
     value = "Hello World!"

     override def value_=(newValue : String) {
        super.value = newValue
        println("Value changed to " + newValue)
     }
   }
 }


Fatally flawed or worth further consideration?

Regards,

Andrew Foggin

--
_____________________________________
/                                                                 \
       /lift/ committer ( www.liftweb.net)
     SGS member (Scala Group Sweden)
 SEJUG member (Swedish Java User Group)
\_____________________________________/

--
_____________________________________
/                                                                 \
       /lift/ committer ( www.liftweb.net)
     SGS member (Scala Group Sweden)
 SEJUG member (Swedish Java User Group)
\_____________________________________/

--
_____________________________________
/                                                                 \

       /lift/ committer ( www.liftweb.net)
     SGS member (Scala Group Sweden)
 SEJUG member (Swedish Java User Group)
\_____________________________________/