Metaprogramming question, alternatives to "class ..."

ruby-talk
1

Folks,

I'm starting to dabble in using some of Ruby's metaprogramming features, in an effort to use actual code in place of configuration files. It's got me to wondering if there's a way to define a method to take the place of a class declaration.

In other words, say I have something like this:

class AddressDataSource < DataSourceBase
   field :name, "customer_name"
   field :address, "cust_addr"
end

....is there any cunning trickery that would allow me to do this:

datasource AddressDataSource
   field :name, "customer_name"
   field :address, "cust_addr"
end

I couldn't think of a way to have a method than can parse up until the matching "end". But, there's a lot of stuff I read here that I wouldn't have thought of myself :slight_smile:

Cheers,
   Kevin

2

Kevin McConnell wrote:

In other words, say I have something like this:

class AddressDataSource < DataSourceBase
  field :name, "customer_name"
  field :address, "cust_addr"
end

...is there any cunning trickery that would allow me to do this:

datasource AddressDataSource
  field :name, "customer_name"
  field :address, "cust_addr"
end

You can have this:

datasource(:AddressDataSource) do
   field :name, "customer_name"
   field :address, "cust_addr"
end

With this:

def datasource(name, &block)
   Object.const_set(name, Class.new(DataSourceBase, &block))
end

Cheers,
  Kevin

Regards,
Florian Gross

3

Florian Gross wrote:

You can have this:

datasource(:AddressDataSource) do
  field :name, "customer_name"
  field :address, "cust_addr"
end

With this:

def datasource(name, &block)
  Object.const_set(name, Class.new(DataSourceBase, &block))
end

That's exactly what I was looking for, thanks.

Cheers,
   Kevin

4

Kevin McConnell wrote:

[snip]

That's exactly what I was looking for, thanks.

Small correction:

def datasource(name, &block)
   module = Module.nesting.first || Object
   module.const_set(name, Class.new(DataSourceBase, &block))
end

That will fix this case:

module X
   datasource(:AddressDataSource) do
     ...
   end
end

Cheers,
  Kevin

Regards,
Florian Gross