ArrayList.propertyMissing ?

[melix]

Hi,

I have a subclass of ArrayList for which I would like to implement propertyMissing. However, I can't figure out how to do this. Seems that Groovy ignores it, while overriding methodMissing works like a charm.

Here's an example :

ArrayList.metaClass.methodMissing = { String name, args->
	println "Ok for method missing"
}
ArrayList.metaClass.propertyMissing = { String name ->
	println "Ok for property missing"
}

def list = []
list.test("ok")
list.test

outputs the following :

Ok for method missing

Is there anything I'm missing ?

[Roshan Dawrani]

For collection objects, ".property" access works a little differently.

For the collection objects "<collection>.<someProperty>" syntax is part of what is called GPath expression language (similar to XPath for XML). It is used to navigate collections in groovy and retrieve all values of a specific attributes from all its members.

Taking an example:

ArrayList.metaClass.methodMissing = {String name, args ->    println "Ok for method missing - $name, $args" }

class MyName{def name; MyName(tmpName) {name = tmpName}}
def list = []

list.test("ok") // invokes methodMissing added on the metaClass above as expected

list << new MyName("Roshan1"); list << new MyName("Roshan2")

// following does not result in propertyMissing as list is collection and instead, it makes a list of "name" property values from all list members

println list.name


In your case, since the list is empty, list.test property also is an empty list.

Another example - "println this.class.methods.name" - return names of all the methods - by making a list of values of the "name" property on every object in the collection returned by "this.class.methods"

rgds,
Roshan

On Wed, Sep 17, 2008 at 9:58 PM, melix <cedric.champeau@...> wrote:

Hi,

I have a subclass of ArrayList for which I would like to implement propertyMissing. However, I can't figure out how to do this. Seems that Groovy ignores it, while overriding methodMissing works like a charm.

Here's an example :

ArrayList.metaClass.methodMissing = { String name, args->
	println "Ok for method missing"
}
ArrayList.metaClass.propertyMissing = { String name ->
	println "Ok for property missing"
}

def list = []
list.test("ok")
list.test

outputs the following :

Ok for method missing

Is there anything I'm missing ?

---

View this message in context: ArrayList.propertyMissing ?
Sent from the groovy - user mailing list archive at Nabble.com.

[melix]

Thanks, but what I'd like is exactly the opposite : in my DSL, I need to be able to override the default propertyMissing method. It seems to be impossible, but I may be wrong.

Roshan Dawrani wrote:

For collection objects, ".property" access works a little differently.

For the collection objects "<collection>.<someProperty>" syntax is part of
what is called GPath expression language (similar to XPath for XML). It is
used to navigate collections in groovy and retrieve all values of a specific
attributes from all its members.

Taking an example:

ArrayList.metaClass.methodMissing = {String name, args ->    println "Ok for
method missing - $name, $args" }

class MyName{def name; MyName(tmpName) {name = tmpName}}
def list = []

list.test("ok") // invokes methodMissing added on the metaClass above as
expected

list << new MyName("Roshan1"); list << new MyName("Roshan2")

// following does not result in propertyMissing as list is collection and
instead, it makes a list of "name" property values from all list members

println list.name


In your case, since the list is empty, list.test property also is an empty
list.

Another example - "println this.class.methods.name" - return names of all
the methods - by making a list of values of the "name" property on every
object in the collection returned by "this.class.methods"

rgds,
Roshan

On Wed, Sep 17, 2008 at 9:58 PM, melix <[e-mail]> wrote:

> Hi,
>
> I have a subclass of ArrayList for which I would like to implement
> propertyMissing. However, I can't figure out how to do this. Seems that
> Groovy ignores it, while overriding methodMissing works like a charm.
>
> Here's an example :
>
> ArrayList.metaClass.methodMissing = { String name, args->
> println "Ok for method missing"
> }
> ArrayList.metaClass.propertyMissing = { String name ->
> println "Ok for property missing"
> }
>
> def list = []
> list.test("ok")
> list.test
>
> outputs the following :
>
> Ok for method missing
>
>
> Is there anything I'm missing ?
> ------------------------------
> View this message in context: ArrayList.propertyMissing ?<http://www.nabble.com/ArrayList.propertyMissing---tp19536068p19536068.html>
> Sent from the groovy - user mailing list archive<http://www.nabble.com/groovy---user-f11867.html>at Nabble.com.
>

[Roshan Dawrani]

Since "collection.property" syntax is used up for providing the GPath expression evaluation feature, I am not sure if you can provide propertyMissing on ArrayList's metaClass and have it called by groovy when you use "collection.anAbsentProperty" syntax.

That is my understanding. However, let's wait for more inputs on this.

rgds,
Roshan

On Wed, Sep 17, 2008 at 11:50 PM, melix <cedric.champeau@...> wrote:

Thanks, but what I'd like is exactly the opposite : in my DSL, I need to be
able to override the default propertyMissing method. It seems to be
impossible, but I may be wrong.

Roshan Dawrani wrote:
>
> For collection objects, ".property" access works a little differently.
>
> For the collection objects "<collection>.<someProperty>" syntax is part of
> what is called GPath expression language (similar to XPath for XML). It is
> used to navigate collections in groovy and retrieve all values of a
> specific
> attributes from all its members.
>
> Taking an example:
>
> ArrayList.metaClass.methodMissing = {String name, args ->    println "Ok
> for
> method missing - $name, $args" }
>
> class MyName{def name; MyName(tmpName) {name = tmpName}}
> def list = []
>
> list.test("ok") // invokes methodMissing added on the metaClass above as
> expected
>
> list << new MyName("Roshan1"); list << new MyName("Roshan2")
>
> // following does not result in propertyMissing as list is collection and
> instead, it makes a list of "name" property values from all list members
>
> println list.name
>
>
> In your case, since the list is empty, list.test property also is an empty
> list.
>
> Another example - "println this.class.methods.name" - return names of all
> the methods - by making a list of values of the "name" property on every
> object in the collection returned by "this.class.methods"
>
> rgds,
> Roshan
>
> On Wed, Sep 17, 2008 at 9:58 PM, melix <cedric.champeau@...>
> wrote:
>
>> Hi,
>>
>> I have a subclass of ArrayList for which I would like to implement
>> propertyMissing. However, I can't figure out how to do this. Seems that
>> Groovy ignores it, while overriding methodMissing works like a charm.
>>
>> Here's an example :
>>
>> ArrayList.metaClass.methodMissing = { String name, args->
>>      println "Ok for method missing"
>> }
>> ArrayList.metaClass.propertyMissing = { String name ->
>>      println "Ok for property missing"
>> }
>>
>> def list = []
>> list.test("ok")
>> list.test
>>
>> outputs the following :
>>
>> Ok for method missing
>>
>>
>> Is there anything I'm missing ?
>> ------------------------------
>> View this message in context: ArrayList.propertyMissing

>> ?<http://www.nabble.com/ArrayList.propertyMissing---tp19536068p19536068.html>

>> Sent from the groovy - user mailing list

>> archive<http://www.nabble.com/groovy---user-f11867.html>at Nabble.com.
>>
>
>

--
View this message in context: http://www.nabble.com/ArrayList.propertyMissing---tp19536068p19538228.html

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[Jochen Theodorou]

melix schrieb:
> Thanks, but what I'd like is exactly the opposite : in my DSL, I need to be
> able to override the default propertyMissing method. It seems to be
> impossible, but I may be wrong.

does it have to be ArrayList? Cant you use a custom class?

bye blackdrag

--
Jochen "blackdrag" Theodorou
The Groovy Project Tech Lead (http://groovy.codehaus.org)
http://blackdragsview.blogspot.com/
http://www.g2one.com/

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[melix]

I do use a custom class (that extends ArrayList) and it doesn't work either. Seems like the propertyMissing method that is used is always the default Groovy one. Looks like a bug to me, but I'd like to be sure ;)

Jochen Theodorou wrote:

melix schrieb:
> Thanks, but what I'd like is exactly the opposite : in my DSL, I need to be
> able to override the default propertyMissing method. It seems to be
> impossible, but I may be wrong.

does it have to be ArrayList? Cant you use a custom class?

bye blackdrag

--
Jochen "blackdrag" Theodorou
The Groovy Project Tech Lead (http://groovy.codehaus.org)
http://blackdragsview.blogspot.com/
http://www.g2one.com/

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[Jochen Theodorou]

melix schrieb:
> I do use a custom class (that extends ArrayList) and it doesn't work either.
> Seems like the propertyMissing method that is used is always the default
> Groovy one. Looks like a bug to me, but I'd like to be sure ;)

it does not even go to property missing. property misssing is kind of
new and the GPath implementation is much older. It is of course an
interesting idea to support gpaths through property missing...

Of course overwriting propertyMissing through user code would then also
mean, that any gpath expression used might no longer work.

bye blackdrag

--
Jochen "blackdrag" Theodorou
The Groovy Project Tech Lead (http://groovy.codehaus.org)
http://blackdragsview.blogspot.com/
http://www.g2one.com/

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[melix]

Well, that's not really a problem in my situation. I'm just pleased that I'm able to setup methodMissing, and it would help me a lot to be able to override propertyMissing too.

Jochen Theodorou wrote:

melix schrieb:
> I do use a custom class (that extends ArrayList) and it doesn't work either.
> Seems like the propertyMissing method that is used is always the default
> Groovy one. Looks like a bug to me, but I'd like to be sure ;)

it does not even go to property missing. property misssing is kind of
new and the GPath implementation is much older. It is of course an
interesting idea to support gpaths through property missing...

Of course overwriting propertyMissing through user code would then also
mean, that any gpath expression used might no longer work.

bye blackdrag

--
Jochen "blackdrag" Theodorou
The Groovy Project Tech Lead (http://groovy.codehaus.org)
http://blackdragsview.blogspot.com/
http://www.g2one.com/

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