R help - Oct 2012 - R5: Lock a class field from within a method?

Hello,

testclass <- setRefClass(
  "testclass",
  fields = list(testfield = "logical"),
  methods = list(validate=function(){testfield<<-TRUE}))
> test <- testclass$new()
> test$testfield
logical(0)
> test$validate()
> test$testfield
[1] TRUE

Works just fine for me.

I would love to be able to do something like

testclass <- setRefClass(
  "testclass",
  fields = list(testfield = "logical"),
  methods = list(validate=function(){
	testfield<<-TRUE
	.self$lock(testfield)
  }))

but am unabel to achieve that. Can anyone point out how to go about 
rendering a field immutable after execution of a specific method?

Sincerely, Joh

On Oct 24, 2012, at 2:14 AM, Johannes Graumann wrote:
> Hello,
>
> testclass <- setRefClass(
>  "testclass",
>  fields = list(testfield = "logical"),
>  methods = list(validate=function(){testfield<<-TRUE}))
>
>> test <- testclass$new()
>> test$testfield
> logical(0)
>> test$validate()
>> test$testfield
> [1] TRUE
>
> Works just fine for me.
>
> I would love to be able to do something like
>
> testclass <- setRefClass(
>  "testclass",
>  fields = list(testfield = "logical"),
>  methods = list(validate=function(){
> 	testfield<<-TRUE
> 	.self$lock(testfield)
>  }))
>
> but am unabel to achieve that. Can anyone point out how to go about
> rendering a field immutable after execution of a specific method?
>
The fact that you used only "lock" in your code and I am unable to  
find such a function makes me wonder whether that was an implicit  
psuedo-code effort and that you do not know about:

?lockBinding

-- 

David Winsemius, MD
Alameda, CA, USA

David Winsemius wrote:
> 
> On Oct 24, 2012, at 2:14 AM, Johannes Graumann wrote:
> 
>> Hello,
>>
>> testclass <- setRefClass(
>>  "testclass",
>>  fields = list(testfield = "logical"),
>>  methods = list(validate=function(){testfield<<-TRUE}))
>>
>>> test <- testclass$new()
>>> test$testfield
>> logical(0)
>>> test$validate()
>>> test$testfield
>> [1] TRUE
>>
>> Works just fine for me.
>>
>> I would love to be able to do something like
>>
>> testclass <- setRefClass(
>>  "testclass",
>>  fields = list(testfield = "logical"),
>>  methods = list(validate=function(){
>> testfield<<-TRUE
>> .self$lock(testfield)
>>  }))
>>
>> but am unabel to achieve that. Can anyone point out how to go about
>> rendering a field immutable after execution of a specific method?
>>
> 
> The fact that you used only "lock" in your code and I am unable
to
> find such a function makes me wonder whether that was an implicit
> psuedo-code effort and that you do not know about:
> 
> ?lockBinding
lockbinding does in fact what I want, but your statement about pseudo-code 
is not entirely correct ... try the following ("?setRefClass" will
light the
way).
> testclass <- setRefClass(
   "testclass",
   fields = list(testfield = "logical"))
> testclass$lock("testfield")
> test <- testclass$new()
> test$testfield <- TRUE
> test$testfield <- FALSE
I was assuming to be able to have access to the "lock" method from a
class
instance as well (rather than just in the class definition) ... Is that 
indeed impossible?

Cheers, Joh