[asp_hornet]

> need a getter

Yeah, thats what I figured. Im not sure if I want the tradeoff of calling .GetValue in multiple places just to save calling validate in maybe 2 or 3 places.

Not to mention I cant easily marshal/unmarshal into it and next week valid username is a username that doesnt already exist in the database.

Maybe this approach appeals to people and Im hesitant to say “that’s not how Go is supposed to be written” but for me this feels like “clever over clear”.

[klodolph]

> Yeah, thats what I figured. Im not sure if I want the tradeoff of calling .GetValue in multiple places just to save calling validate in maybe 2 or 3 places.

The tradeoff is not that you save calling validate, it’s that you avoid forgetting to call validate in the first place, because when you forget to validate, you get a type error.

IMO it’s a little more clear this way:

    type Ticket struct {
      requestor Username
      assignee  Username
    }

It lets you write code that is little more obvious.

[asp_hornet]

I’m not sure I understand. In your example you’ve grouped related data in a struct and validating that it matches your system’s invariants, that feels good to me.

The original example was more “wrap a simple type in an object so it’s always validated when set” which looks beautiful when you don’t have the needed getters in the example nor show all the Get call sites opposed to the 1 or 2 New call sites. All in the name of “we don’t want to set the username without validation” but without private constructors Username{“invalid”} can be invoked, the validation circumvented and I’m not convinced the overhead we paid was worth it.

[Sakos]

The countless bugs I've had to deal with and all the time I've lost fixing these bugs caused by people who forgot to validate data in a certain place or didn't realize they had to do so proves to me that the overhead of calling a get on a wrapper type is totally worth it.

I value the hours wasted on diagnosing a bug far more than the extra keystrokes and couple of seconds required to avoid it in the first place.

[asp_hornet]

No, you’ve achieved an illusion of that as now your spending hours wasted on discovering where a developer forgot to call NewUsername and instead called Username{“broken”}. I cant see the value in this abstraction in Go.

[iampims]

They can’t because value is not exported. They must use the NewUsername function, which forces the validation.

In my opinion, this pattern breaks when the validation must return an error and everything becomes very verbose.

[asp_hornet]

Oh, thats true about it being unexported. I hadn’t considered that.