Checking the parameters "type"

ruby-talk
1

Hi all,

I’ve trying to find out how to check the class of a parameter. Right, I
talking about this:

class TestClass
# arg1 must be String instance
def myMethod(arg1, arg2)
# Code, code and more code.
end
end

I think that I could solve in this way:

class TestClass
# arg1 must be a String instance
def myMethod(arg1, arg2)
if not arg1.kind_of?(String)
# Error! Some code must be added!
end
end
end

Right, we are going to suppose now that I want to add an Integer as attribute
(myAttribute):

class TestClass
attr_writer :myAttribute
…
end

This attribute must be writable. But, there’s a little trouble:
How could I assure that the parameter passed to myAttribute= method is
Integer? Must I implement the method by myself?

class TestClass
def myAttribute=(value)
if not myAttribute
end
end

Can it be automatized in some way?

Thank you all very much!

···

–
Imobach González Sosa
imodev@softhome.net
osoh@jabber.org

2

look on raa for types.rb and strongtyping modules. These will make it
easy for you to check types and will give you some more goodies ( like
kind of MMD )

···

il Fri, 30 Jan 2004 05:44:26 +0900, “Imobach González Sosa” imodev@softhome.net ha scritto::

Hi all,

I’ve trying to find out how to check the class of a parameter. Right, I
talking about this:

3

Hi!

  • Imobach González Sosa:

Hi all,

I’ve trying to find out how to check the class of a parameter. Right, I
talking about this:

class TestClass

arg1 must be String instance

def myMethod(arg1, arg2)
# Code, code and more code.
end
end

I think that I could solve in this way:

class TestClass

arg1 must be a String instance

def myMethod(arg1, arg2)
if not arg1.kind_of?(String)
# Error! Some code must be added!
end
end
end

Try this:

class TestClass
def myMethod(arg1, arg2)
unless arg1.class == String
raise ArgumentError.exception(‘first argument must be string’)
end
puts arg1, arg2
end
end

Test:

test = TestClass.new
test.myMethod(‘foo’, ‘bar’)
test.myMethod(1, ‘bar’)

How could I assure that the parameter passed to myAttribute= method
is Integer?

Why not? It is easy to define a setter:

class TestClass
def myAttribute=(value)
if value.class <= Integer
@myAttribute = value
else
raise ArgumentError.exception(‘assignment requires integer’)
end
end

def myAttribute
@myAttribute
end
end

I did add a getter so that testing is possible.

test = TestClass.new
test.myAttribute = 10
puts test.myAttribute
test.myAttribute = ‘foo’
puts test.myAttribute

Question to community: Raise an ArgumentError or a TypeError?

Josef ‘Jupp’ SCHUGT

···

–
http://oss.erdfunkstelle.de/ruby/ - German comp.lang.ruby-FAQ
http://rubyforge.org/users/jupp/ - Ruby projects at Rubyforge
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Germany 2004: To boldly spy where no GESTAPO / STASI has spied before

4

Thank you gabriele and Jupp for your answers. At this moment, I’m trying
StrongTyping, and it seems to work just fine for my purposes.

See ya!

···

El Jueves, 29 de Enero de 2004 22:44, gabriele renzi escribió:

il Fri, 30 Jan 2004 05:44:26 +0900, “Imobach González Sosa” > > imodev@softhome.net ha scritto::

Hi all,

I’ve trying to find out how to check the class of a parameter. Right, I
talking about this:

look on raa for types.rb and strongtyping modules. These will make it
easy for you to check types and will give you some more goodies ( like
kind of MMD )