# Why the object doesn't respond to its method?

**URL:** <https://www.ruby-forum.com/t/why-the-object-doesnt-respond-to-its-method/150757>\
**Category:** Ruby\
**Created:** [October 12, 2008, 7:35pm UTC](https://www.ruby-forum.com/t/why-the-object-doesnt-respond-to-its-method/150757 "2008-10-12T19:35:37Z")\
**Posts on this page:** 9\
**Page:** 1

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**Author:** ![alex-osu3](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/13edae/32.png) [@alex-osu3](https://www.ruby-forum.com/u/alex-osu3)\
**Post date:** [October 12, 2008, 7:35pm UTC](https://www.ruby-forum.com/t/why-the-object-doesnt-respond-to-its-method/150757/1 "2008-10-12T19:35:37Z")

</div>

Hi all,

I want to find out if an object responses to a method. while I can tell  
that the excel object(in this script) responses to method ‘Visible or  
visible’, my codes DO NOT come true. Any idea?

Thank very much,

Li

C:\Users\Alex\>irb  
irb(main):001:0\> require ‘win32ole’  
=\> true  
irb(main):002:0\>  
irb(main):003:0\* excel=WIN32OLE.new(“excel.application”)  
=\> #WIN32OLE:0x389d638  
irb(main):004:0\> excel.Visible=true  
=\> true  
irb(main):005:0\> puts excel.respond\_to?(“visible”)  
false  
=\> nil  
irb(main):006:0\> puts excel.respond\_to?(“Visible”)  
false  
=\> nil  
irb(main):007:0\>  
irb(main):008:0\* puts excel.respond\_to?(‘visible’)  
false  
=\> nil  
irb(main):009:0\> puts excel.respond\_to?(‘Visible’)  
false  
=\> nil  
irb(main):010:0\>  
irb(main):011:0\* puts excel.respond\_to?(:visible)  
false  
=\> nil  
irb(main):012:0\> puts excel.respond\_to?(:Visible)  
false  
=\> nil  
irb(main):013:0\>

---

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**Author:** ![alex-osu3](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/13edae/32.png) [@alex-osu3](https://www.ruby-forum.com/u/alex-osu3)\
**Post date:** [October 12, 2008, 7:47pm UTC](https://www.ruby-forum.com/t/why-the-object-doesnt-respond-to-its-method/150757/2 "2008-10-12T19:47:58Z")

</div>

Li Chen wrote:

> Hi all,
> 
> I want to find out if an object responses to a method. while I can tell  
> that the excel object(in this script) responses to method ‘Visible or  
> visible’, my codes DO NOT come true. Any idea?

My guess is that WIN32OLE handles the call to Visibile via  
method\_missing and  
does not redefine respond\_to? to return true for methods handled by  
method\_missing.  
Or, given that in your code you only ever called Visible= and never just  
Visible, it might actually be the case that it does not respond to  
Visible,  
though that is admittedly unlikely.

HTH,  
Sebastian

---

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**Author:** ![alex-osu3](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/13edae/32.png) [@alex-osu3](https://www.ruby-forum.com/u/alex-osu3)\
**Post date:** [October 12, 2008, 8:00pm UTC](https://www.ruby-forum.com/t/why-the-object-doesnt-respond-to-its-method/150757/3 "2008-10-12T20:00:31Z")

</div>

Li Chen wrote:

> Hi all,
> 
> I want to find out if an object responses to a method. while I can tell  
> that the excel object(in this script) responses to method ‘Visible or  
> visible’, my codes DO NOT come true. Any idea?

Hello. First, in your code you actually do not call the method Visible,  
you call the method Visible= and it’s a big difference, generally.

But you won’t find the method Visible= neither, as, as said above, the  
capitalised ole methods are handled by method\_missing. You can see a  
list of ole methods like this:  
excel.ole\_methods  
This gives an array of all the methods, where you can see Visible twice,  
once it is the method Visible and once Visible=, but you cannot tell one  
from another at a glance. To get just a list of, say, setters, to find  
the method Visible=, you write excel.ole\_put\_methods, and to get a list  
of getters (or probably other methods, but with exclusion of setters)  
you write excel.ole\_get\_methods.

Now there’s one more problem - the list doesn’t contain strings, but  
WIN32OLE\_METHOD objects. I do not actually know how to handle this, but  
this is how you can check if Visible= is among the methods of the  
object:  
excel.ole\_put\_methods.find{|m| m.name==“Visible”}  
The above line returns nil iff excel does not respond to Visible=.

TPR.

---

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**Author:** ![alex-osu3](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/13edae/32.png) [@alex-osu3](https://www.ruby-forum.com/u/alex-osu3)\
**Post date:** [October 12, 2008, 11:23pm UTC](https://www.ruby-forum.com/t/why-the-object-doesnt-respond-to-its-method/150757/4 "2008-10-12T23:23:19Z")

</div>

Li Chen wrote:

> Hi Thomas,
> 
> I find the method “Visible” but not"Visible=" here but the  
> respond\_to?(“Visible”) still return false. I don’t know how to explain  
> it.

This is correct. As it has been said, the respond\_to? doesn’t work with  
ole methods as they are served by metod\_missing, which means that there  
are no such methods defined for this object. A sample to illustrate  
this:

class K  
def method\_missing(m)  
puts “Inside qwe” if m==:qwe  
end  
end  
k=K::new  
k.respond\_to? :qwe #=\> false  
k.qwe ## prints: Inside qwe

So you are not able to check if there is an ole method using  
respond\_to?. I hoped I stated it clearly in the above post, but  
apparently not.

Now the other problem: when you write excel.Visible=true, you call the  
method Visible=, but, as already stated, respond\_to? :Visible= will not  
detect the presence of this method. You have to look for this method in  
the ole\_methods table.

In general, ole methods are divided into two groups - setters (those  
that you call with = at the end, like Visible=) and other methods (those  
without =, like when you call excel.Visible (it returns the current  
status) or any other of similar methods. But in the ole\_methods table,  
they are all reported without the =, that’s why you see two elements  
Visible in the table returned by excel.ole\_methods. To distinguish  
between them, it’s better to look up the method you are looking for in  
the specific ole methods table, so: you look for setters inside  
excel.ole\_put\_methods, and for other methods inside  
excel.ole\_get\_methods. So, to check if there is a method called Visible  
(without =, the getter), you run this code:  
excel.ole\_get\_methods.find{|m| m.name==“Visible”}  
It returns nil if the method is not present and calling excel.Visible  
will raise an error, and a non-nil value if the ole method is present.  
But if you want to check if there is a setter, that is, a method named  
Visible=, then you have to look it up in the other table:  
excel.ole\_put\_methods.find{|m| m.name==“Visible”}  
Again, nil means no method, non-nil means that method Visible= is  
present for the object. Note that in the last code line there is no  
“Visible=”, but “Visible”, and this is because ole setters in the ole  
methods table do not have the = in name, even though they are setters.  
And that’s the very reason why we must look up setters and getters in  
two distinct tables.

If you want, you can add a method like ole\_respond\_to? to the class  
WIN32OLE, like this:

class WIN32OLE  
def ole\_respond\_to?(m)  
m=m.to\_s  
if m[-1]==?=  
m=m[0…-1]  
table=ole\_put\_methods  
else  
table=ole\_get\_methods  
end  
!!table.find{|om| om.to\_s==m}  
end  
end

excel.ole\_respond\_to? :Visible= #=\> true

Not tested carefully, so rather don’t use it unless you can understand  
it.

Hope this helps.

TPR.

---

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**Author:** ![alex-osu3](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/13edae/32.png) [@alex-osu3](https://www.ruby-forum.com/u/alex-osu3)\
**Post date:** [October 13, 2008, 12:34am UTC](https://www.ruby-forum.com/t/why-the-object-doesnt-respond-to-its-method/150757/5 "2008-10-13T00:34:44Z")

</div>

Hi Thomas,

Thank you very much for the detailed explanation.

It is my understanding from your reply that I should look for  
ole\_get\_methods for the methods of “getter” and look for ole\_put\_methods  
for methods of “setter”.

Question 1: In the following scripts both getters and setters have  
method “Voice” but respond\_to?() responses to both of them as “fasle”.  
It seems to me that respond\_to?() cannot detect the methods in either  
getters or setters. Is it true? If this is case what methods can be  
detected by respond\_to?() ?

Question 2: There are ole\_put\_methods, ole\_get\_methods, and ole\_methods  
in WIN32OLE. From your post now I know the differences among  
ole\_put\_methods and ole\_get\_methods. But how about ole\_methods? I only  
know it will return more methods. And most of them cannot detected by  
respond\_to?(),either.

Li

C:\Users\Alex\>irb  
irb(main):001:0\> require ‘win32ole’  
=\> true  
irb(main):002:0\>  
irb(main):003:0\* voice=WIN32OLE.new(‘SAPI.SpVoice’)  
=\> #WIN32OLE:0x280e934  
irb(main):004:0\>  
irb(main):005:0\* puts “1-getters”  
1-getters  
=\> nil  
irb(main):006:0\> puts

=\> nil  
irb(main):007:0\> puts voice.ole\_get\_methods.sort{|x,y|x.to\_s\<=\>y.to\_s}  
AlertBoundary  
AllowAudioOutputFormatChangesOnNextSet  
AudioOutput  
AudioOutputStream  
EventInterests  
Priority  
Rate  
Status  
SynchronousSpeakTimeout  
Voice  
Volume  
=\> nil  
irb(main):008:0\> puts

=\> nil  
irb(main):009:0\>  
irb(main):010:0\* puts “2-setters=”  
2-setters=  
=\> nil  
irb(main):011:0\> puts

=\> nil  
irb(main):012:0\> puts voice.ole\_put\_methods.sort{|x,y|x.to\_s\<=\>y.to\_s}  
AlertBoundary  
AllowAudioOutputFormatChangesOnNextSet  
AudioOutput  
AudioOutputStream  
EventInterests  
Priority  
Rate  
SynchronousSpeakTimeout  
Voice  
Volume  
=\> nil  
irb(main):013:0\> puts

=\> nil  
irb(main):014:0\>  
irb(main):015:0\* puts “respond to 1-getters”  
respond to 1-getters  
=\> nil  
irb(main):016:0\> puts voice.respond\_to?(“Voice”)  
false  
=\> nil  
irb(main):017:0\>  
irb(main):018:0\* puts “respond to 2-setters=”  
respond to 2-setters=  
=\> nil  
irb(main):019:0\> puts voice.respond\_to?(“Voice”)  
false  
=\> nil  
irb(main):020:0\>

---

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**Author:** ![alex-osu3](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/13edae/32.png) [@alex-osu3](https://www.ruby-forum.com/u/alex-osu3)\
**Post date:** [October 12, 2008, 11:04pm UTC](https://www.ruby-forum.com/t/why-the-object-doesnt-respond-to-its-method/150757/6 "2008-10-12T23:04:46Z")

</div>

Thomas B. wrote:

> > Now there’s one more problem - the list doesn’t contain strings, but  
> > WIN32OLE\_METHOD objects. I do not actually know how to handle this, but  
> > this is how you can check if Visible= is among the methods of the  
> > object:  
> > excel.ole\_put\_methods.find{|m| m.name==“Visible”}  
> > The above line returns nil iff excel does not respond to Visible=.
> 
> TPR.

Hi Thomas,

I find the method “Visible” but not"Visible=" here but the  
respond\_to?(“Visible”) still return false. I don’t know how to explain  
it.

Li

C:\Users\Alex\>irb  
irb(main):001:0\> require ‘win32ole’  
=\> true  
irb(main):002:0\>  
irb(main):003:0\* excel=WIN32OLE.new(“excel.application”)  
=\> #WIN32OLE:0x398d638  
irb(main):004:0\>  
irb(main):005:0\*  
irb(main):006:0\* puts “first method”  
first method  
=\> nil  
irb(main):007:0\> excel.ole\_get\_methods.each do |e|  
irb(main):008:1\* if “#{e}”==“Visible”  
irb(main):009:2\> puts “find Visible”  
irb(main):010:2\> elsif “#{e}”==“Visible=”  
irb(main):011:2\> puts “find Visible=”  
irb(main):012:2\> else  
irb(main):013:2\* #puts “no method”  
irb(main):014:2\* end  
irb(main):015:1\> end  
find Visible  
=\> [Application, …MANY METHODS HERE… HighQualityModeForGraphics]  
irb(main):016:0\>  
irb(main):017:0\* puts “second methods”  
second methods  
=\> nil  
irb(main):018:0\> excel.ole\_put\_methods.each do |e|  
irb(main):019:1\* if “#{e}”==“Visible”  
irb(main):020:2\> puts “find Visible”  
irb(main):021:2\> elsif “#{e}”==“Visible=”  
irb(main):022:2\> puts “find Visible=”  
irb(main):023:2\> else  
irb(main):024:2\* #puts “no method”  
irb(main):025:2\* end  
irb(main):026:1\>  
irb(main):027:1\* end  
find Visible  
=\> [ActivePrinter,…MANY METHODS HERE…  
LargeOperationCellThousandCount,HighQualityModeForGraphics]  
irb(main):028:0\>  
irb(main):029:0\* puts excel.respond\_to?(“Visible”)  
false  
=\> nil  
irb(main):030:0\>

---

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**Author:** ![alex-osu3](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/13edae/32.png) [@alex-osu3](https://www.ruby-forum.com/u/alex-osu3)\
**Post date:** [October 13, 2008, 7:36pm UTC](https://www.ruby-forum.com/t/why-the-object-doesnt-respond-to-its-method/150757/7 "2008-10-13T19:36:58Z")

</div>

HI Thomas,

Thank you very much for your time and the help.

Li

---

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**Author:** ![alex-osu3](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/13edae/32.png) [@alex-osu3](https://www.ruby-forum.com/u/alex-osu3)\
**Post date:** [October 13, 2008, 9:26am UTC](https://www.ruby-forum.com/t/why-the-object-doesnt-respond-to-its-method/150757/8 "2008-10-13T09:26:32Z")

</div>

Li Chen wrote:

> It seems to me that respond\_to?() cannot detect the methods in either  
> getters or setters. Is it true? If this is case what methods can be  
> detected by respond\_to?() ?

The ole methods cannot be detected by respond\_to?. This is exactly what  
I have been trying to communicate to you, since the first post.

In general, respond\_to? detects all methods of all object. Ole objects  
are sort of exception here - ole methods are not detected by  
respond\_to?, but other methods are. If you have any object of any of the  
standard Ruby classes, it will always work as expected - respond\_to?  
returns true iff the object responds to this method.

> But how about ole\_methods? I only  
> know it will return more methods. And most of them cannot detected by  
> respond\_to?(),either.

It just returns all the ole methods, both setters and non-setters, all  
messed up together. You will see that excel.ole\_methods includes a  
method named Visible twice - one of them is the setter and the other is  
the getter. The only way to tell which is which (the only that I know  
for now, but note that I was never really working with ole objects) is  
to call the method’s return\_type method, like this:

irb(main):075:0\> voice.ole\_methods.select{|m| m.to\_s==“Voice”}.each{|m|  
p m.return\_type\_detail}  
[“PTR”, “USERDEFINED”, “ISpeechObjectToken”]  
[“VOID”]

But I don’t know how to interpret the results. But we at least see now  
that these are two distinct methods, even though both are reported to be  
named Voice.

TPR.

---

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**Author:** ![alex-osu3](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/13edae/32.png) [@alex-osu3](https://www.ruby-forum.com/u/alex-osu3)\
**Post date:** [October 14, 2008, 4:59pm UTC](https://www.ruby-forum.com/t/why-the-object-doesnt-respond-to-its-method/150757/9 "2008-10-14T16:59:51Z")

</div>

Hi Thomas,

I guess I figure out why the object doesn’t respond to its method in  
win32ole.

Based on my other post this week someone points to me that I need to  
pass more parameters into the method.

Please see the following scripts:  
Ruby will complain if I write fs.Open(file) but it works if another  
parameter 2 is passed.

But right now I still can’t figure out how to pass the right  
parameter(in this sample is 2).

Li

###############################  
require ‘win32ole’  
fs=WIN32OLE.new(‘SAPI.SpFileStream’)

p fs.ole\_method(“open”).params

file=‘c:/test.txt’

fs.Open(file,2) #least two params  
fs.write(“data”)  
fs.Close