mORMot Open Source

LarsS

Member

Registered: 2014-04-25

Posts: 4

Non-framework error/result handling with services as methods

Hi,

I have been looking a lot at the mORMot documentation lately as well as making some demo projects. I think it is a great framework! and have started to use it in one or our projects.

I am focusing on the "services as methods" side and not the ORM/DB. I will need to create 3-6 "services" interfaces and each of these will have from 10-50 methods.

I am trying to figure out a good common error/result reporting "mechanism" to use consistently for all these methods.
By error/result reporting I mean how you return information about the method call to the caller. Not errors in the framework, connection etc.
e.g. a method like

  procedure AddProduct(aID: string; aName: string; aType: Integer);

could result in errors like:
- Invalid ID/Name/Type
- Product already exists
- Not allowed

My current idea is to use a "generic" record for all methods. Something like

type
  TCallResult = packed record
    Error: Integer
    Severity: TSeverityEnum;
    Text: string;
  end;

  procedure AddProduct(aID: string; aName: string; aType: Integer; out Result: TCallResult);

  or

  function AddProduct(aID: string; aName: string; aType: Integer): TCallResult;

- Is this a "good" way to implement it or is there a better way (maybe part of the framework)?
- Is using the "out" parameter better/worse than using a function with the record as the result?

br Lars

ab

Administrator

From: France

Registered: 2010-06-21

Posts: 14,659

Website

Re: Non-framework error/result handling with services as methods

You can do this.
It perfectly does make sense.

There is no difference by using an "out" or a function result, for records: in fact, a function result is implemented like a last "out" parameter.

By default, a record will be serialized as text.
A somewhat better may be to use text-based JSON serialization, to have the TCallResult serialized as plain JSON, so will be much able to be consumed with any client (e.g. AJAX).

Thanks for the feedback.