A tiny bit of metaprogramming magic

[wtd]

Ruby:

class <<Object         define_method :delegate do |ivar, *mnames|                 mnames.each do |mname|                         instance_eval do                                 define_method mname do |*args|                                         instance_variable_get(:"@#{ivar}").send(mname, *args)                                 end                         end                 end         end end

A simple demo:

Ruby:

class Foo         delegate :bar, :abs         def initialize                 @bar = -1         end end

Now:

Ruby:

Foo.new.abs

Will yield:

code:

1

[gianni]

Tres cool, this kind of stuff makes me feel all warm and fuzzy inside.

[gianni]

My small contribution based entirely off of wtd's code:

Ruby:

class <<Object   define_method :delegalias do |ivar, alias_name, meth|     instance_eval do       define_method alias_name do |*args|         instance_variable_get(:"@#{ivar}").send(meth, *args)       end     end   end end

Demo:

Ruby:

class Foo   delegalias :person, :to_s, :inspect     def initialize     @person = {:name => "John Smith", :id => 1402, :email => "jsmith@domain.tld"}   end end

Ruby:

Foo.new.to_s

Yields:

code:

"{:name=>\"John Smith\", :email=>\"jsmith@domain.tld\", :id=>1402}"

[wtd]

Most excellent.

[Insectoid]

tres confused.

I am completely lost, though with under a week (or has it been a week?) of Ruby experience, that is to be expected. What does class <<object do? What does 'delegate' do?

[wtd]

In Ruby classes are objects. By using "class <<Object" I am working within the context of the class rather than instances of it.

As for delegate, it is just a method, but one on the class, rather than instances of it. What it does is to define a method on instances of the class.

code:

>> class <<Object >>         define_method :delegate do |ivar, *mnames| ?>                 mnames.each do |mname| ?>                         instance_eval do ?>                                 define_method mname do |*args| ?>                                         instance_variable_get(:"@#{ivar}").send(mname, *args) >>                                 end >>                         end >>                 end >>         end >> end => #<Proc:0x082f0960@(irb):2> >> class Foo >>    def initialize >>       @bar = -32 >>    end >> end => nil >> Foo.delegate(:bar, :abs) => [:abs] >> a = Foo.new => #<Foo:0x82e9160 @bar=-32> >> a.abs => 32 >>

The equivalent manual code would be:

code:

class Foo    def abs(*args)       @bar.abs(*args)    end end

[Cowzero]

Is a great knowledge