Newbie: Reflection question(?)

[Gaudi Mi]

At runtime I have the name of a class in a string, and I want to call a
method on the class having that name. How do I do that?

E.g., let's say that we have several classes that all have a method
called address().
At run-time I know I want to call the method address() on a particular
class, and that class name is in a string.

Thanks.
G

 

[Kev Jackson]

At runtime I have the name of a class in a string, and I want to call a
method on the class having that name. How do I do that?

E.g., let's say that we have several classes that all have a method
called address().
At run-time I know I want to call the method address() on a particular
class, and that class name is in a string.

you need to look at call

eg to instantiate an object (call Object.new)

m = c.methodnew)
o = m.call

to call address method

m = c.methodaddress)
m.call

Kev

 

[Gaudi Mi]

I'll try that, thanks Kev!

G

you need to look at call

eg to instantiate an object (call Object.new)

m = c.methodnew)
o = m.call

to call address method

m = c.methodaddress)
m.call

Kev

 

[Ross Bamford]

At runtime I have the name of a class in a string, and I want to call a
method on the class having that name. How do I do that?

Here are two possible ways:

str = "Array"
# => "Array"

ary_clz = eval(str)
# => Array

ary_clz.class
# => Class

ary_clz.new
# => []

##################

ary_clz = Object.const_get(str)
# => Array

ary_clz.new
# => []

 

[Robert Klemme]

At runtime I have the name of a class in a string, and I want to call a
method on the class having that name. How do I do that?

Here are two possible ways:

str = "Array"
# => "Array"

ary_clz = eval(str)
# => Array

ary_clz.class
# => Class

ary_clz.new
# => []

##################

ary_clz = Object.const_get(str)
# => Array

ary_clz.new
# => []

const_get is definitely preferred as it doesn't show the same security
risks as eval does.

Addtional note, for nested class names:

name.split(/::/).inject(Object) {|cl,n| cl.const_get(n)}.address()

Kind regards

robert

 

[Benjohn Barnes]

you need to look at call

eg to instantiate an object (call Object.new)

m = c.methodnew)
o = m.call

I don't think that's going to work for him (if c is the
name_of_class_string that he's got). He needs to look up the class
named name_of_class_string:

ObjectSpace.const_get(name_of_class_string).new(*any_arguments)

I'd like to check that is the "right way" to do it, but I don't have
any reference books to hand.