Messages from Usenet group comp.lang.idl-pvwave, compiled by Paulo Penteado
There is no way except what you already mentioned. IDLitComponent::GetPropertyByIdentifier isn't written in IDL but is an internal routine. Cheers, marc
Robert Barnett writes: > I've been trying to write my own classes which incorporate IDLitComponent and widget_propertysheet. This allows the user to tinker with object properties via a GUI, > > I'm very confused by IDLitComponent::GetPropertyByIdentifier. The method allows you to do a "ClassName::GetProperty, Name=Value", > however "Name" is only known at runtime. > > For example > > obj -> GetPropertyByIdentifier("BoringProperty", empty_variable) > > somehow triggers > > obj -> GetProperty, BORINGPROPERTY=empty_variable > > This is something that I would very much like to do with my own classes without having to inherit IDLitComponent. > > To be more precise, does anyone know how IDLitComponent::GetPropertyByIdentifier tricks the arg_present() > function into thinking that a keyword needs to be set? Here is a quick and dirty explanation of how this can be done. The actual code is a *bit* more complicated then this, but not much more complicated. In any case, this will be enough to get you started. The main trick is to define an output variable on the *__DEFINE procedure so you can get the class structure easily. All depends on that. :-) ;*********************************************************** **** PRO Object_Trick::GetProperty, _Ref_Extra=extra Object_Trick__Define, class properties = Tag_Names(class) keyword = (extra)[0] index = Where(properties EQ keyword, count) IF count GT 0 THEN BEGIN (Scope_Varfetch(keyword, /Ref_Extra)) = self.(index) ENDIF END FUNCTION Object_Trick::INIT self.thick = 2 self.linestyle = 4 RETURN, 1 END PRO Object_Trick__Define, class class = { Object_Trick, $ THICK:0, $ LINESTYLE:0 } END ;*********************************************************** **** Then, IDL> obj = Obj_New('Object_Trick') IDL> obj -> GetProperty, Linestyle=linestyle & Print, linestyle 4 IDL> obj -> GetProperty, Thick=thick & Print, thick 2 I'll leave it as an exercise for the reader to write the generic SetProperty method. :-) Cheers, David (Hint: Google the IDL archives for SCOPE_VARFETCH.) -- David Fanning, Ph.D. Fanning Software Consulting, Inc. Coyote's Guide to IDL Programming: http://www.dfanning.com/
I'm soon to send a feature request to RSI about it. What do you think about the following procedures? ;CallGetProperty.pro ;+ ; NAME: ; CallGetProperty ; ; PURPOSE: ; To get the property of an object, when the keyword is only known at runtime. ; ; CATEGORY: ; Introspection ; ; CALLING SEQUENCE: ; CallGetProperty, obj, kwd, value ; ; INPUTS: ; obj: The object from which to obtain the property ; kwd: The keyword name of the property ; ; OUTPUTS: ; value: The value of the property ; ; SIDE EFFECTS: ; Expects to be able to make a single call "obj -> GetProperty" ; ; EXAMPLE: ; ; ; Define an object ; ; pro boringobj__define ; struct = {boringobj, boringproperty: ''} ; end ; ; pro boringobj::GetProperty, BORINGPROPERTY=boringproperty ; if (arg_present(boringproperty)) then $ ; boringproperty = self.boringproperty ; end ; ; ; Get its property ; ; CallGetProperty, obj_new('boringobj'), 'BORINGPROPERTY', value ; print, value ; ;- pro CallGetProperty, obj, kwd, value ; Unknown implementation end ;CallSetProperty.pro ;+ ; NAME: ; CallSetProperty ; ; PURPOSE: ; To set the property of an object, when the keyword is only known at runtime. ; ; CATEGORY: ; Introspection ; ; CALLING SEQUENCE: ; CallSetProperty, object, kwd, value ; ; INPUTS: ; object: The object from which to obtain the property ; kwd: The keyword name of the property ; value: The value of the property ; ; SIDE EFFECTS: ; Expects to be able to make a single call "obj -> SetProperty" ; ; EXAMPLE: ; ; ; Define an object ; ; pro boringobj__define ; struct = {boringobj, boringproperty: ''} ; end ; ; pro boringobj::SetProperty, BORINGPROPERTY=boringproperty ; if (n_elements(boringproperty) gt 0) then $ ; self.boringproperty = boringproperty ; end ; ; ; Set its property ; ; CallSetProperty, obj_new('boringobj'), 'BORINGPROPERTY', 'boring value' ; ;- pro CallSetProperty, obj, kwd, value obj -> SetProperty, _EXTRA=create_struct(kwd, value) end ============================================================ =========== The actual application I had in mind was a configuration tool. I have objects with properties which I would like to be able to edit via a GUI at runtime. I can do this very effectively by using widget_propertysheet. However, I have numerous objects and do not want to bother setting up a widget_propertysheet for each object individually. Instead, I wish to query objects for properties which are 'IDLContainer's and automatically generate a widget_tree based on the links between objects. -- nrb@ Robbie Barnett imag Research Assistant wsahs Nuclear Medicine & Ultrasound nsw Westmead Hospital gov Sydney Australia au +61 2 9845 7223
But what is the problem with execute? I think this cries for it. marc
m_schellens@hotmail.com writes: > But what is the problem with execute? > I think this cries for it. Virtual Machine. :-) Cheers, David -- David Fanning, Ph.D. Fanning Software Consulting, Inc. Coyote's Guide to IDL Programming: http://www.dfanning.com/
Well it is kinda nice that I can run my application on the IDL VM http://www.zipworld.com.au/~retsil/idl/rt_launcherconfig_tes t1.sav This is an example application. It is a configuation tool which allows me to create and maintain a configuration tree according to the relationships between various classes. It's simply not possible (or at least efficent) to do this kind of thing without introspection. Hence, I've made much use of IDLitComponent::GetPropertyByIdentifier. Thanks for all your responses. ------------------------------------------------------------ ----- There are some days when IDL just spoils all the fun and puts up a random brick wall saying "No! You can't do that.". After tearing my hair out over an otherwise insignificant issue I come to this newsgroup for a bit of (syntax) therapy. I'm very glad that we're all nice to each other round here. -- Robbie --