Noob: Review code for us of object orientation

Ruby
1

Would appreciate is if someone could look over the attached file which
contains two modules.

I have a large number of old Cobol files to convert into a MySQL
database. The programs work upto this point and I have not added the
code to move the result into MySQL yet. It merely prints the hash of
the binary file so far.

I am just starting to learn Ruby and OOP as well and am more concerned
that I am bringing to much of my procedural coding style into my OOP
programs.

Comments, suggestions and advice welcomed.

Len

2

On 02/16/2010 05:58 PM, Len S. wrote:

programs.

Comments, suggestions and advice welcomed.

I believe it looks pretty good already. I think you have grokked OO
basics, although you could have more classes - something which often
happens when starting with OO. In your case I would add these classes

RecordField = Struct.new :name, :type, :length, :decimal

aropnfil = [
RecordField[‘cust_no’, :Xstr:, 6, 0],
RecordField[‘doc_date’, :Date, 6, 0],
…
]

Also I’d use Symbols rather than String for the type qualifiers (or even
class objects, if that’s possible) because they are more efficient than
String (you typically have only few values and each repeats quite a
bit).

Your record_length is redundant if I’m not mistaken (it’s the sum of all
field lengths). So I’d probably also add a class for the complete
record description.

RecordDefinition = Struct.new :record_fields do
def initialize(fields = [])
self.record_fields = fields
end

def record_length
record_fields.inject(0) {|sum, rd| sum + rd.length}
end
end

aropnfil = RecordDefinition.new [
RecordField[‘cust_no’, :Xstr:, 6, 0],
RecordField[‘doc_date’, :Date, 6, 0],
…
]

I would then model WangFile’s interface similar to File and include
Enumerable

def WangFile

def self.foreach(*a, &b)
wf = open(*a)
begin
wf.each_record(&b)
ensure
wf.close
end
end

def self.open(*a)
new(*a)
end

def close
…
end

def initialize(file_name, record_definition)
…
end

include Enumerable

def each_record
len = record_definition.record_length

 while buffer = ....read(len)
   yield(parse_record(buffer))
 end

 self

end

alias each each_record
end

And a minor detail: you can save typing by doing

hash_record[name] = case type
when :Xstr
@record[start,len]
when :Xint
@record…

Kind regards

robert