Class Module

[Wesley Silva]

Hi, I'm still learning ruby and i'm trying, but I just can't understand
this result...

class Module
@@docs = {}
# Invoked during class definitions
def doc(str)
@@docs[self.name] = self.name + ":\n" + str.gsub(/^\s+/, '')
end
# invoked to get documentation
def Module::doc(aClass)
# If we're passed a class or module, convert to string
# ('<=' for classes checks for same class or subtype)
aClass = aClass.name if aClass.class <= Module
@@docs[aClass] || "No documentation for #{aClass}"
end
end
class Example
doc("This is a sample documentation string")

# .. rest of class
end

puts Module::doc(Example)


Produces:

Example:
This is a sample documentation string


But

class Module
@@docs = {}
# Invoked during class definitions
def doc(str)
@@docs[self.name] = self.name + ":\n" + str.gsub(/^\s+/, '')
end
# invoked to get documentation
def Module::doc(aClass)
# If we're passed a class or module, convert to string
# ('<=' for classes checks for same class or subtype)
aClass = aClass.name if aClass.class <= Module
@@docs[aClass] || "No documentation for #{aClass}"
end
end
class Example<Module
doc("This is a sample documentation string")

# .. rest of class
end

puts Module::doc(Example)

Produces:

No documentation for Example


Can anybody tell me why?

 

[David A. Black]

Hi --

Hi, I'm still learning ruby and i'm trying, but I just can't understand
this result...

class Module
@@docs = {}
# Invoked during class definitions
def doc(str)
@@docs[self.name] = self.name + ":\n" + str.gsub(/^\s+/, '')
end
# invoked to get documentation
def Module::doc(aClass)
# If we're passed a class or module, convert to string
# ('<=' for classes checks for same class or subtype)
aClass = aClass.name if aClass.class <= Module
@@docs[aClass] || "No documentation for #{aClass}"
end
end
class Example
doc("This is a sample documentation string")

# .. rest of class
end

puts Module::doc(Example)


Produces:

Example:
This is a sample documentation string


But

class Module
@@docs = {}
# Invoked during class definitions
def doc(str)
@@docs[self.name] = self.name + ":\n" + str.gsub(/^\s+/, '')
end
# invoked to get documentation
def Module::doc(aClass)
# If we're passed a class or module, convert to string
# ('<=' for classes checks for same class or subtype)
aClass = aClass.name if aClass.class <= Module
@@docs[aClass] || "No documentation for #{aClass}"
end
end
class Example<Module
doc("This is a sample documentation string")

# .. rest of class
end

puts Module::doc(Example)

Produces:

No documentation for Example


Can anybody tell me why?

When you do this:

class Example < Module
doc("string")
end

the doc method you're calling is Module.doc. The object Example has
two doc methods in its method lookup path, and that's the one it hits
first.

If you change Module.doc to Module.show_doc (or whatever), you'll see
the difference.


David

 

[Wesley Silva]

Thanks a lot David!

I would like to make another question please...

If i just change Modules's name for Father for example:

class Father
@@docs = {}
def doc(str)
@@docs[self.name] = self.name + ":\n" + str.gsub(/^\s+/, '')
end
def Father::show_doc(aClass)
aClass = aClass.name if aClass.class <= Module
@@docs[aClass] || "No documentation for #{aClass}"
end
end
class Example<Father
doc("This is a sample documentation string")
end

puts Father::show_doc(Example)

Produces:

undefined method `doc' for Example:Class (NoMethodError)

Can you tell why?

 

[David A. Black]

Hi --

Thanks a lot David!

I would like to make another question please...

If i just change Modules's name for Father for example:

class Father
@@docs = {}
def doc(str)
@@docs[self.name] = self.name + ":\n" + str.gsub(/^\s+/, '')
end
def Father::show_doc(aClass)
aClass = aClass.name if aClass.class <= Module
@@docs[aClass] || "No documentation for #{aClass}"
end
end
class Example<Father
doc("This is a sample documentation string")
end

puts Father::show_doc(Example)

Produces:

undefined method `doc' for Example:Class (NoMethodError)

Can you tell why?

doc is an instance method of Father, and Example is not an instance of
Father (it's an instance of Class). So you can't call doc on Example.


David

 

[Robert Klemme]

Hi --

Thanks a lot David!

I would like to make another question please...

If i just change Modules's name for Father for example:

class Father
@@docs = {}
def doc(str)
@@docs[self.name] = self.name + ":\n" + str.gsub(/^\s+/, '')
end
def Father::show_doc(aClass)
aClass = aClass.name if aClass.class <= Module
@@docs[aClass] || "No documentation for #{aClass}"
end
end
class Example<Father
doc("This is a sample documentation string")
end

puts Father::show_doc(Example)

Produces:

undefined method `doc' for Example:Class (NoMethodError)

Can you tell why?

doc is an instance method of Father, and Example is not an instance of
Father (it's an instance of Class). So you can't call doc on Example.

Wesley, IMHO there is an easier as well as safer solution: safer,
because a class's name may be unset. Also, your solution keeps
documentation of all classes in memory even if they are GC'ed (if that's
possible, I am not sure). So here's what I'd do:

class Module
def doc(str = nil)
if str
@doc = (name + ":\n" + str.strip).freeze
else
@doc
end
end
end

Kind regards

robert

 

[David Masover]

Also, your solution keeps
documentation of all classes in memory even if they are GC'ed (if that's
possible, I am not sure).

I hope it's possbile to GC a class, otherwise Class#new can be a memory leak.